On paper, the Red Sox feature three locks in their rotation and what seems like about a dozen question marks whom the team hopes to re-shape into a couple of answers.

Given that the failures of the rotation played a central role in the team’s collapse in 2011, it has been natural to view the team’s financially conservative approach to rotation building with some skepticism. Rather than pursuing an obvious (and pricey) upgrade, the Sox to date have brought a number of potentially cost-effective solutions into the mix.

The team’s approach to the construction of its rotation is partly a function of its payroll limits and partly a function of its comfort with the front three of Jon Lester, Josh Beckett and Clay Buchholz, three pitchers who -- if healthy -- have potentially dominating stuff.

As good as Lester, Beckett and Buchholz can be (again, with the caveat that they must remain healthy -- not a given based on the fact that all three missed time due to injury in 2011, and that Beckett and Buchholz have missed significant time on the DL in recent seasons), it is worth asking: Are the Sox being too cavalier with the back of their rotation?

Put another way: The Sox’ goal is to compete for a championship. That being the case, what kind of back-end starters do World Series-winning teams have, and where do they come from?

The 2011 Cardinals offer an interesting case-study in the making of a championship rotation. The team made a mid-year adjustment to its rotation, adding Edwin Jackson in a trade. In October, they featured four starters (Chris Carpenter, Jaime Garcia, Kyle Lohse, Edwin Jackson) who had been good rather than great.

None were All-Stars. All featured ERAs that were slightly better than league average but not significantly so, with all four finishing the season with an ERA+ (the pitcher’s ERA as compared to the league average) that was better than 100 but less than 110.

In some respects, this year’s Cardinals team had an unusual profile for a World Series winner. The absence of starting pitchers who had been dominant during the regular season was atypical.

Of the 17 World Series winners since the advent of the divisional round of the playoffs in 1995, 10 (59 percent) have had at least three pitchers with an ERA+ of 110 or better (meaning ERAs that were at least 10 percent better than league average). All but two of the last 17 World Series winners (88 percent) have had at least two such pitchers.

That said, just four (24 percent) have had four postseason starters who had an ERA+ of 110 or better during the regular season. In that sense, it would appear that a dominant No. 4 starter is more unusual than it is common for championship teams.

In that respect, the 2011 Cardinals were very much in line with precedent. Last season’s St. Louis team also featured a number of additional shared traits with prior championship rotations. Among them:

-- A mid-year alteration to the rotation. Of the last 17 World Series winners, 11 (65 percent) have featured a postseason starter who wasn’t with the team in the majors at the beginning of the year. Five of those teams made trades; seven received at least one start in October from a pitcher who was called up after the start of the season.

-- A solid fourth starter. While recent championship teams typically have not featured dominant Game 4 starters in the postseason, they usually do feature a fourth starter who is roughly league average. Of the last 17 World Series winners, 10 (59 percent) have had four starters with an ERA+ of 100 or better.

So what does all of that mean for the Red Sox? There are a couple of implications.

First, if the Sox can have a healthy and productive Lester, Beckett and Buchholz joined by one league-average starter from their wide-ranging mix of candidates for the last two spots in the rotation, then they will feature a rotation that aligns with the type of starting groups that has proven capable of winning championships. In all likelihood, the team doesn’t need an ace, but rather just a solid, reliable contributor who can keep the team in the game on a predictable basis.

Secondly, there is a reasonable chance that the Sox will need to identify some kind of second-half reinforcement for their rotation. That said, championship teams haven’t had to trade for top-of-the-rotation starters. Instead, moves have been made to acquire the likes of Edwin Jackson, Joe Blanton, Jeff Weaver, Albie Lopez and Denny Neagle -- not exactly a list of future Hall of Famers.

That being the case, the sensibility of the Sox’ emphasis on depth is apparent. Championship teams have viable alternatives when one of their season-opening starting options falter. The 2011 Red Sox, ultimately, did not.

The 2012 edition of the club, while short on dazzling names, hopes to correct that deficiency, whether with once-solid performers such as Vicente Padilla, Aaron Cook or Carlos Silva or even with an almost-forgotten reinforcement such as Daisuke Matsuzaka, whose conditioning work to recover from Tommy John surgery is producing raves.

Will it work? Check back in October.

That said, if the Red Sox set their bar according to the construction of a championship-caliber rotation (rather than, say, trying to match the Yankees on a move-for-move basis), then the logic of the team’s approach to this offseason becomes a bit clearer.

Here is a year-by-year look at the pitchers who made postseason starts for the last 17 World Series winners (with regular season ERA and ERA+ in parentheses):

2011 Cardinals

Chris Carpenter (3.45 ERA, 105 ERA+), Jaime Garcia (3.56 ERA, 102 ERA+, Kyle Lohse (3.39 ERA, 107 ERA+), Edwin Jackson (3.58 ERA, 102 ERA+)

Notable change: The Cardinals acquired Jackson, Octavio Dotel, Corey Patterson and Marc Rzepcynski from the Blue Jays at the trade deadline for Colby Rasmus, Trever Miller, Brian Tallet and P.J. Walters.

2010 Giants

Matt Cain (3.14 ERA, 124 ERA+), Tim Lincecum (3.43 ERA, 114 ERA+), Jonathan Sanchez (3.07 ERA, 127 ERA+), Madison Bumgarner (3.00 ERA, 131 ERA+)

Notable change: The Giants called up Bumgarner in late-June, resulting in their entirely homegrown championship rotation.

2009 Yankees (three-man rotation in postseason)

CC Sabathia (3.37 ERA, 137 ERA+), A.J. Burnett (4.04 ERA, 114 ERA+), Andy Pettitte (4.16 ERA, 111 ERA+)

Notable change: None, unless one counts the decision by the Yankees to go with the three-man rotation in October.

2008 Phillies

Cole Hamels (3.09 ERA, 142 ERA+), Jamie Moyer (3.71 ERA, 118 ERA+), Joe Blanton (4.20 ERA, 105 ERA+), Brett Myers (4.55 ERA, 97 ERA+)

Notable change: The Phillies traded for Blanton in July, giving up a three-player package of prospects Josh Outman, Adrian Cardenas and Matt Spencer.

2007 Red Sox

Josh Beckett (3.27 ERA, 145 ERA+), Curt Schilling (3.87 ERA, 123 ERA+), Daisuke Matsuzaka (4.40 ERA, 108 ERA+), Tim Wakefield (4.76 ERA, 100 ERA+), Jon Lester (4.57 ERA, 104 ERA+)

Notable change: Lester was called up in July.

2006 Cardinals

Chris Carpenter (3.09 ERA, 144 ERA+), Jeff Suppan (4.12 ERA, 108 ERA+), Jeff Weaver (5.18 ERA, 86 ERA+), Anthony Reyes (5.06 ERA, 88 ERA+)

Notable change: The Cardinals acquired Weaver in a July salary dump by the Angels in exchange for outfielder Terry Evans. The team also called up right-hander Reyes from the minors.

2005 White Sox

Jose Contreras (3.61 ERA, 125 ERA+), Mark Buehrle (3.12 ERA, 144 ERA+), Freddy Garcia (3.87 ERA, 116 ERA+), Jon Garland (3.50 ERA, 128 ERA+)

Notable change: None. All four of those starters made at least 32 starts.

2004 Red Sox

Curt Schilling (3.26 ERA, 150 ERA+), Pedro Martinez (3.90 ERA, 125 ERA+), Bronson Arroyo (4.03 ERA, 121 ERA+), Derek Lowe (5.42 ERA, 90 ERA+)

Notable change: None, though Arroyo ended up replacing Byung-Hyun Kim in the rotation when the latter was injured early in the season.

2003 Marlins

Josh Beckett (3.04 ERA, 138 ERA+), Brad Penny (4.13 ERA, 102 ERA+), Dontrelle Willis (3.30 ERA, 127 ERA+), Mark Redman (3.59 ERA, 117 ERA+), Carl Pavano (4.30 ERA, 98 ERA+)

Notable change: Willis was called up in May, shortly after A.J. Burnett was lost for the year due to Tommy John surgery.

2002 Angels

Jarrod Washburn (3.15 ERA, 141 ERA+), Kevin Appier (3.92 ERA, 113 ERA+), Ramon Ortiz (3.77 ERA, 118 ERA+), John Lackey (3.66 ERA, 121 ERA+)

Notable change: Lackey made his big-league debut at the end of June and never left the rotation, finishing the year by starting (and winning) Game 7 of the World Series.

2001 Diamondbacks

Curt Schilling (2.98 ERA, 157 ERA+), Randy Johnson (2.49 ERA, 188 ERA+), Miguel Batista (3.36 ERA, 139 ERA+), Albie Lopez (4.00 ERA, 117 ERA+) Brian Anderson (5.20 ERA, 90 ERA+)

Notable changes: Acquired Lopez catcher Mike Difelice from the Devil Rays for Nick Bierbrodt and Jason Conti at the trade deadline. Batista shuttled between the rotation and bullpen all season.

2000 Yankees

Andy Pettitte (4.35 ERA, 111 ERA+), Roger Clemens (3.70 ERA, 131 ERA+), Orlando Hernandez (4.51 ERA, 107 ERA+), David Cone (6.91 ERA, 70 ERA+), Denny Neagle (5.81 ERA, 83 ERA+)

Notable change: Acquired Neagle and Mike Frank from the Reds for Jackson Melian, Drew Henson and Ed Yarnall in July.

1999 Yankees

Roger Clemens (4.60 ERA, 103 ERA+), David Cone (3.44 ERA, 137 ERA+), Orlando Hernandez (4.12 ERA, 115 ERA+), Andy Pettitte (4.70 ERA, 101 ERA+)

Notable change: None.

1998 Yankees

David Wells (3.49 ERA, 127 ERA+), David Cone (3.55 ERA, 125 ERA+), Orlando Hernandez (3.13 ERA, 142 ERA+), Andy Pettitte (4.24 ERA, 104 ERA+)

Notable change: Orlando Hernandez, who signed just before the start of the regular season, was called up in June.

1997 Marlins

Kevin Brown (2.69 ERA, 150 ERA+), Livan Hernandez (3.18 ERA, 128 ERA+), Alex Fernandez (3.59 ERA, 113 ERA+), Al Leiter (4.34 ERA, 93 ERA+), Tony Saunders (4.61 ERA, 88 ERA+)

Notable change: Hernandez was called up mid-season, entering the rotation for good at the end of June.

1996 Yankees

David Cone (2.88 ERA, 175 ERA+), Jimmy Key 4.68 ERA, 107 ERA+), Andy Pettitte (3.87 ERA, 129 ERA+), Kenny Rogers (4.68 ERA, 107 ERA+)

Notable change: None, though Cone missed roughly four months of the season before returning in September.

1995 Braves

Greg Maddux (1.63 ERA, 262 ERA+), Tom Glavine (3.08 ERA, 139 ERA+), John Smoltz 3.18 ERA, 135 ERA+), Steve Avery (4.67 ERA, 92 ERA+)

Notable change: None.