There were few jobs more hazardous in the NBA last season than reserve player for the Celtics. Marquis Daniels underwent surgery on his spinal cord, Delonte West fractured his wrist and the O’Neal’s – Jermaine and Shaq – injured almost everything else. Kendrick Perkins spent more that half the season rehabbing from knee surgery, and his replacement, Nenad Krstic, suffered bone bruises on both knees after he arrived from Oklahoma City.

In early April, Kevin Pelton from Basketball Prospectus estimated that the Celtics had lost 233 games and almost 5,000 minutes to injuries. Other teams had it worse. The Bucks and Blazers in particular were decimated last season, but what made the Celtics situation unique is that the vast majority of their injury problems were related to their second-line players.

Kevin Garnett sat out only nine games because of injury and Paul Pierce and Ray Allen didn’t miss any (they were held out of the final two games of the regular season). But all those ailments did have an effect on the starters as an ineffective bench rotation forced Doc Rivers to rely on his stars too much when early leads were quickly erased and deficits became larger.

That has to change this year. Rivers needs his bench to stay healthy, obviously, but they also have to be effective and able to function without help from Pierce, Allen, Garnett and Rajon Rondo. “If we can get away with one of them on the floor and still play well, that’s huge,” Rivers said.

Under normal circumstances, Rivers prefers to use eight or nine players, but with 66 games in just 124 days, set rotations have been replaced by flexibility and versatility. Danny Ainge added Keyon Dooling, Brandon Bass and Chris Wilcox and brought back Marquis Daniels and Sasha Pavlovic. All of them can guard more than one position and younger players like Avery Bradley, E’twaun Moore and JaJuan Johnson will also have the chance to compete for playing time.

Sunday’s exhibition game offered a glimpse of how Rivers intends to mix things up. The idea is to play faster with more fullcourt pressure defense and halfcourt traps – something the Celtics have shied away from in the past -- leading to better transition opportunities. That will mean more substitutions, quirkier lineups and shorter rotations.

The Celtics still have two roster spots available. Ainge may not be done adding to the roster, but he’s limited to offering the veteran minimum and the remaining free agent pool is thin. Greg Stiemsma has been the most impressive of the camp invites and he offers size and shot-blocking ability. He’s put himself in position to contend for a roster spot. Gilbert Brown, Jamal Sampson and Michael Sweetney face an uphill climb with limited practice reps.

Here’s how the pieces line up at the moment behind Rondo, Allen, Pierce, Garnett and Jermaine O’Neal:

Point guard: Dooling
Wings: Daniels, Moore, Bradley, Pavlovic
Big Men: Bass, Wilcox, Johnson

THE VETERANS

Keyon Dooling: The Celtics have been trying to acquire Dooling for years. Rivers loves his versatility, professionalism and intensity.

“I’ve always liked his grit,” Rivers said. “He reminds me of a guy I had in Orlando, Darrell Armstrong. He’s feisty. He’s tough. He can guard the one or the two, he makes big shots, he’s clever. He’s not a pure point. He can play both positions.”

Dooling isn’t a pure point guard, but he offers the best backup that Rondo has had the last four years. He’s not a great shooter -- Dooling made 42 percent of his 3-pointers in New Jersey in 2008-09, then saw his average drop from 38 to 35 percent the last two seasons in Milwaukee – but he has confidence in his shot and he knows how to play. He’ll be the first guard off the bench and he’ll also play off the ball in some of their offensive sets.

Brandon Bass: The comparisons to Glen Davis are obvious -- they’re both undersized big men who grew up together and played at LSU. Both were second round picks who had to earn their playing time and they both averaged a little more than 11 points and 5 rebounds per game last season. Their roles will also be similar, yet they are completely different players.

Bass is a much better offensive player, with the ability to step out and make jump shots and he has the strength and athleticism to finish inside, especially on the break. Those traits are invaluable for the Celtics, but Bass isn’t in the same class defensively as Davis.

Rivers likes the combination of Garnett and Bass because both of them can spread the floor offensively with their shooting ability and defensive matchups will be based on the opponent. Bass is the key reserve in their frontcourt rotation.

Marquis Daniels: The Celtics were thrilled to bring Daniels back and they’re confident that he is fully recovered from spinal cord surgery. Without Jeff Green, Daniels is Pierce’s primary backup at small forward and he could see time at the other guard position as well.

His game is well known to Celtics fans, but expect him to be used in more post-up situations this season. He’s an excellent cutter, which helps their halfcourt offense and he’s a good enough passer and facilitator to initiate the offense, which would free up Dooling to play off the ball. (Colleague Ben Rohrbach offers a more in-depth look at Daniels’ return).

Chris Wilcox: The Celtics used their taypayer mid-level exception to sign Wilcox to a one-year contract. It’s the perfect deal for a player whose production hasn’t always matched his talent.

“We’ve got to get something out of Chris,” Rivers said. “I think he can really play. I don’t think he’s ever really had to play. He’s never been in the playoffs. If we can get him to have a mind change he can be good for us.”

Wilcox has had periods of brilliance throughout his career. He was fantastic down the stretch with the Pistons once he finally got a chance to play regular minutes, but it’s been four years since he put up back-to-back seasons of 13 points and 7 rebounds. Wilcox does almost all of his damage inside. He’s a good offensive rebounder who can also expect his share of fast-break passes from Rondo in transition.

Sasha Pavlovic: His return seemed curious, but in light of the revelations regarding Green, bringing him back for one more year makes sense. The Celtics have vivid memories of the way he played in 2008 for the Cavaliers during the playoffs, but he hasn’t been nearly as effective in recent years.
At 6-foot-7, he has the size and toughness to guard wing players. If nothing else, he’ll provide veteran insurance behind Pierce and Allen.

THE YOUNG PLAYERS

Avery Bradley: On the one hand the Celtics think Bradley can be an elite defender. Not good, elite. On the other, the point guard experiment is over and in order to use his defense, Bradley has to provide a competent level of offense when he’s on the court. In many ways the comparisons to a young Tony Allen are apt.

But Bradley is so quick that he can get to the free throw line off the dribble and that’s a decent starting point for a player who just turned 21 and had precious little experience in college or the pros. His development is a work in progress.

E’Twaun Moore: The second round pick from Purdue arrived in camp fresh off a strong stint in Europe, playing for famed Benetton Treviso. He’s played well in camp, winning over both his coaches and his veteran teammates. No player has done more to help his cause in the short camp than Moore.

He dropped in the draft because he’s a little small for the off guard position and he isn’t really a point guard. But the Celtics like that he isn’t afraid to seize the moment – his two late jumpers against the Raptors on Sunday are the most recent example – and there is opportunity for playing time behind Ray Allen.

JaJuan Johnson: There was no mystery why the team’s first round pick didn’t see any action until the fourth quarter on Sunday. Johnson is simply behind the other four players in the frontcourt rotation and Rivers’ top priority is getting ready for the start of the season. Johnson will get his chances, but he’s clearly behind the four veterans up front.