For the last three months, the focus, naturally, has been on addressing the Red Sox' most obvious roster voids. The Sox entered the winters with needs at numerous positions -- first base, both outfield corners, starting rotation, potentially shortstop. Nine free agent signings later, those holes have been addressed.

But while all the roster holes have been covered, what lies beneath the roster surface? The acquisition of Mike Napoli -- a player with the ability to be a force in the middle of the lineup but with a physical ailment that was of sufficient concern to turn his three-year agreement into a one-year deal -- to serve as the team's primary first baseman offers something of a reminder about the challenges of roster-building.

The Red Sox have been slammed in recent years by a wealth of devastating injuries that they were ill-prepared to absorb. Of course, that's not a surprise -- it would have been nearly impossible for any team to endure the loss of roughly half of its everyday lineup for much of the year.

Indeed, at times, depth proved a strength of the 2012 Sox. Will Middlebrooks emerged as a formidable big league regular when Kevin Youkilis went down and both Pedro Ciriaco and Daniel Nava displayed big league skill sets that allowed the team to stay above water for a time despite the onset of injuries.

Even so, there was a point -- specifically, when David Ortiz suffered an injury to his right Achilles that cost him almost all of the final two-plus months of the year -- when the proverbial dam broke. The team simply couldn't replace his elite production.

The struggle to score in his absence underscored an important notion: Often, the question of how well prepared a team is to absorb the loss of one of its stars is as important as the fact that the team has the star. Given the inevitability of injuries over the course of a 162-game season, roster depth -- the ability to sustain performance even without a full complement of players -- is a critical component of a team's success.

So how deep are the 2013 Sox? Who are the players behind the starters who might determine whether the team can weather the proverbial storm with, say, a .500 stretch while one of its regulars is on the DL?

The team seems to feel as if it's reasonably well covered to withstand the typical attrition of a season.

"I think from an overall standpoint, as it relates to the whole roster, we're in pretty good shape," said manager John Farrell.

But what does that mean? Here is a look at how the team's depth chart is shaping up, with the assumption that the bench is likely to feature catcher David Ross, utility man Pedro Ciriaco, outfielder Ryan Sweeney and another player -- perhaps not yet signed -- who can play first as well as either third base or the outfield.

DESIGNATED HITTER

Starter: David Ortiz

Alternatives: Mike Napoli, Jonny Gomes, Ryan Lavarnway, Mauro Gomez

Through July 26, with a healthy Ortiz, the Red Sox enjoyed incredible production from their designated hitters, who amassed a .301/.397/.561 line with 20 homers, with almost all of that damage coming from Ortiz. From that point through the end of the season, with Ortiz's Achilles injury permitting him to play just one game, the team had paltry production from that offensive position, with Sox DHs hitting .246/.304/.347.

For the most part, however, neither Lavarnway nor Gomez served as DH. Lavarnway spent most of his time behind the plate. Gomez got the lion's share of his playing time at first or third base.

Both profile as legitimate big league hitters. Though Lavarnway struggled in the big leagues last year, he has a consistent track record of power and patience in the minor leagues that had talent evaluators of multiple big league clubs suggesting he was/is ready to be an everyday big league DH in 2011. That hasn't changed. Two bad months in the big leagues shouldn't alter that assessment.

Still, it's a nice luxury for the Sox to have another hitter such as Gomez available as a depth option. He wasn't a dominant hitter by any stretch in the big leagues, but after abusing Triple-A pitching en route to the International League MVP, he held his own in the majors, hitting .275/.324/.422/.746, offering roughly league average production in limited playing time.

His presence permits the Sox to go with the proverbial hot hand at DH, as either he or Lavarnway could be called up (or inserted into the starting lineup) as a DH, depending on who is most locked in at a given time.

It would be unrealistic not to expect a considerable dropoff if Ortiz goes down. All the same, with two potential in-house candidates to fill in for him (along with the option of sliding Mike Napoli to DH and featuring either Gomez or Mark Hamilton at first base, or having Jonny Gomes DH with either Ryan Sweeney or Daniel Nava in left), the Sox should be positioned to get adequate production from the position if Ortiz is sidelined.

CATCHER

Starter: Jarrod Saltalamacchia

Alternative(s): David Ross, Ryan Lavarnway

This is a position of most pronounced depth for the Sox. Saltalamacchia has become a known quantity, a player with huge power and inconsistent on-base abilities. Ross has been one of the more productive catchers in the big leagues over the last four years, hitting .269/.353/.463/.816. While that production has come in a part-time role, the Sox would feel comfortable with him going from a backup to a frontline option if Saltalamacchia were to get injured. The same is true of Lavarnway. As such, the Sox are not only covered in terms of depth, but also maintain the ability to explore trades using surplus at the position.

FIRST BASE

Starter: Mike Napoli

Alternative(s): Mauro Gomez, Mark Hamilton, Daniel Nava

This is admittedly the position where the Sox' depth is most lacking, a considerable issue given that -- even though his avascular necrosis has yet to present symptoms -- there are questions about Napoli's ability to play a full season.

The Sox recognize that reality, which is why they're still likely to add another player capable of serving as a fallback at that position.

"The one area that we probably need to get a feel for is at first base," said manager John Farrell. "We fully expect Napoli to be ready to go, but if a need were to arise at that position, I think we'll probably have some additions before camp opens up in that area, so that there will be protection provided at first base."

Hamilton has struggled in a very small sample of big league at-bats, hitting .197/.258/.246/.503 in 66 plate appearances in 2010-11. However, he's shown a good approach and some pop in the minors (an average of 24 homers per 162 games along with a .277/.364/.468/.832 line).

Still, the Sox would seemingly like more options at first base. The team does plan to have switch-hitter Daniel Nava get some work at first in the spring, though it remains to be seen how he will take to the position.

SECOND BASE

Starter: Dustin Pedroia

Alternative(s): Pedro Ciriaco, Brock Holt

Pedroia is, of course, a surpassing talent. Still, when he went down last year, Ciriaco was able to deliver solid offense and defense for the Sox before his lack of plate discipline got exposed in a larger sample. Meanwhile, the Sox acquired Holt from the Pirates in the Joel Hanrahan deal because he offers a professional left-handed hitter who can play either middle infield position.

As with Ortiz, the dropoff from Pedroia to anyone else at second base would be pronounced. Even so, the Sox view Ciriaco and Holt as capable of solid production as fill-ins.

THIRD BASE

Starter: Will Middlebrooks

Alternative(s): Pedro Ciriaco, Brock Holt

Ciriaco and Holt both offer respectable production for middle infielders, but neither will be confused for having the power of a corner. A year ago, when Middlebrooks went down with a broken wrist in August, the combination of his absence along with that of Ortiz left gaping voids in the Sox' lineup.

Ciriaco can handle the defensive demands of playing third base, while Holt -- who has only played at shortstop and second base in his career to date -- will get some work at third base in spring training to see if he can be a backup there.

Still, given the offensive demands of the two infield corners, one understands why the Sox were so interested in adding Eric Chavez before he elected to sign with Arizona. In some respects, the perfect roster complement at this point would be a left-handed hitting first baseman/third baseman. It remains to be seen if that player is out there. (Aubrey Huff remains a free agent, though he hasn't played third base since 2008, and he's considered defensively limited at both corners; he's also struggled offensively in the last two years after a huge 2010 season.)

Beyond Ciriaco and Holt, at some point during the year, there's a chance that Xander Bogaerts could represent a depth option at third, especially if he shows aptitude at the position for the Netherlands while preparing for the World Baseball Classic.

SHORTSTOP

Starter: Stephen Drew

Alternative(s): Jose Iglesias, Pedro Ciriaco, Brock Holt

The roster value of Ciriaco becomes increasingly apparent as one goes up and down the roster to realize how many positions he can back up, at least as a stopgap. Still, in all likelihood, if Drew were to be sidelined for more than a couple of games, the Sox would seem more inclined to call up Iglesias and benefit from his electric defense than to stick with Ciriaco on an everyday basis.

After all, until Drew was signed, the Sox viewed Iglesias as the top in-house option. In doing so, they acknowledged that while the 23-year-old's offense remains a work in progress, his glove is so special that he can be an asset rather than a detriment even if his offense is limited (presuming that last year's struggles -- a .118/.200/.191/.391 line -- represented an exaggerated view of his offensive abilities).

Again, Bogaerts could factor into the shortstop depth equation as the season progresses, particularly depending on team needs. If, for instance, the rest of the lineup is healthy and producing up to expectations, then the Sox could afford to emphasize run prevention (Iglesias) over run production (Bogaerts). But, if the team has a couple of injuries that are threatening the overall production of the lineup, then the appeal of having an offense-minded shortstop in the lineup -- in a hypothetical scenario in which Drew was unavailable -- would increase.

OUTFIELD

Starters: Jacoby Ellsbury, Jonny Gomes, Shane Victorino

Alternative(s): Ryan Sweeney, Daniel Nava

For now, the Sox appear inclined to go with four outfielders to start the year and to focus on another first base option to round out a bench that is most likely to feature catcher David Ross, Ciriaco and a first baseman (with positional versatility) to be identified. The ability of Victorino to play either right or center field insulates the Sox a bit, offering a credible alternative in the middle of the outfield should Jacoby Ellsbury miss time.

The re-signing of Sweeney to a minor league deal that includes an opt-out before the end of spring training positions him as the odds-on favorite to make the club as the fourth outfielder for opening day, ahead of Nava (who has options remaining).

And while Sweeney saw his production tumble last year following a concussion (at the time of that injury, he was hitting .311/.341/.443/.784; thereafter, he hit .183/.247/.268/.515), his career suggests that he's a hitter capable of posting competitive at-bats with decent on-base percentages even if expectations for his power are modest. He's also capable of offering above-average defense at all three outfield positions, making him a valuable fourth outfielder and left-handed complement to Jonny Gomes.

That is not to downplay the ability of Nava, who offered tremendous production and a strong on-base presence for a month-plus last year before a succession of wrist injuries began to erode his numbers. He also made considerable strides defensively in the outfield.

If he can add the ability to play first base to his resume, then as a switch-hitter who can play outfield and first while doing posting strong OBPs against right-handed pitchers (.261/.369/.399/.768 vs. right-handers compared to .191/.302/.318/.621 against lefties), Nava is a valuable depth option, particularly on a team that skews right-handed.

Beyond those five outfielders, the team also features a pair of highly regarded prospects with a chance to make an impact at the big league level this year. Both Bryce Brentz and Jackie Bradley Jr. look like future big league starters; at some point in 2013, they could be called upon to fill in for an injured starter, with Brentz capable of offering depth to the outfield corners while Bradley is already big league-ready defensively in center field.

However, Alex Hassan, might be the first depth option behind Sweeney and Nava, given that he was added to the 40-man roster this winter. (Neither Brentz nor Bradley is on the 40-man roster yet, and Bradley has spent just two months in Double-A, while Brentz has played for just a couple weeks in Triple-A.) Hassan has a career .391 OBP in parts of four minor league seasons and already has a full season in Triple-A on his resume, and is a right-handed hitter who is capable of backing up either outfield corner.

In other words, on paper, the Sox have better depth now in the outfield than they did a year ago, when simultaneous injuries to Ellsbury, Carl Crawford and Cody Ross left the team scrambling to get players from outside the organization, including Marlon Byrd and Scott Podsednik. There's a nice mix of prospects with high ceilings who represent something of an unknown and players who have demonstrated an ability to offer solid production over stretches in the big leagues.

STARTING PITCHING

Starters: Jon Lester, Clay Buchholz, Ryan Dempster, John Lackey, Felix Doubront

Alternative(s): Rubby De La Rosa, Allen Webster, Stephen Wright, Chris Hernandez

With Lackey out for all of 2012 following Tommy John surgery and the Sox financially constrained in their quest to round out their rotation, last year, the team entered spring training without an identified fourth or fifth starter. Though Doubront emerged as a solid big league starter, Daniel Bard's performance as a member of the rotation proved a disaster. The back of the rotation ended up being a considerable weakness, and the team simply never received sustained positive impact from depth options like Daisuke Matsuzaka or Aaron Cook.

This year, the shape of the rotation is more promising. The addition of Ryan Dempster and return of Lackey, at least in theory, has the rotation looking more stable entering spring training. At the same time that they'll improve the organization's depth from the top, the team is also seeing its ranks swell further down.

In addition to the two veterans who will be in the rotation in Dempster and Lackey, the team also has a crop of young, intriguing starters who are now in Triple-A, including a pair (Rubby De La Rosa, Allen Webster) with stuff that ranks with anyone in the system. They also have a knuckleballer (Stephen Wright) who has shown promising early returns in his effort to come to grips with the pitch.

"At least on paper, starting-wise, we're deeper than we were a year ago, particularly with younger guys who are going to provide additional depth," said Farrell. "Whether that's Stephen Wright with the knuckleball, whether that's [Allen] Webster, whether that's [Rubby] De La Rosa, I think there's a better overall feel for starting depth."

In this case, there's a lot of ceiling with little certainty for those three pitchers (all of whom are on the 40-man roster) given the degree of unpredictability that can accompany players graduating from the minors to the big leagues -- particularly given that Wright (knuckleball), Webster (sinker) and De La Rosa (triple-digit fastball) all lean on pitches that can be difficult to command.

Still, the fact that the team has multiple pitchers with electric stuff who will be in Triple-A at the start of the year is a distinct contrast to the scenario that confronted the Sox a year ago.

Chris Hernandez, while not as prominent a name and not on the 40-man roster, has shown a consistent ability to compete with a feel for pitching that allows his modest stuff to play up. The fact that he'll be in big league camp underscores his standing in the organization.

BULLPEN

Big leaguers: Joel Hanrahan, Andrew Bailey, Junichi Tazawa, Koji Uehara, Craig Breslow, Andrew Miller, Franklin Morales, Daniel Bard (?), Alfredo Aceves (?), Clayton Mortensen (?)

Alternative(s): Alex Wilson

If one includes Daniel Bard (who has options), Alfredo Aceves (who also has an option) and Clayton Mortensen (out of options), then the Red Sox feature 10 viable bullpen options for seven spots to start the season, with another pitcher who is just about big league ready (Wilson) right behind them. This should be an area of strength if Hanrahan and/or Bailey are pitching close to their previous All-Star forms, and if Tazawa and/or Uehara continue to post freakish strikeout-to-walk numbers with the stuff and deception to dominate in the late innings.

"Bullpen I think pretty much speaks for itself, and not just from a current surplus, but from a couple arms that are going to be able to be called upon if needed," said Farrell.