One of the great speculative themes you find in any spring training occurs when we ask “can he come back?” about any given player rehabbing from injury. The answer for Chris Carpenter is “yes,” because he’s done this before. But if you ask “can he come back again?” the answer is less clear. Carpenter is such a unique case with a unique combination of circumstances that he demands a nuanced look, not only at how his problems mesh together, but at how his strengths might help him return to the mound.

Once upon a time, Carpenter was one of the Blue Jays‘ best young pitchers, a tall New Englander teaming up with Roger Clemens and Pat Hentgen to form the front men in a solid rotation. Subsequently, his career never reached the heights or the longevity of that pair of former teammates. By 2001, while some were looking for a new Jays mini-dynasty with Carpenter teaming up with Roy Halladay to lead the rotation, Carpenter’s arm was in tatters. He went from Opening Day starter to non-tendered in the space of a single season. Carpenter had a torn labrum, an injury that, at the time, was seen as a professional death sentence for pitchers.

Undeterred, the Cardinals took a shot on Carpenter, knowing that it was only the shoulder that was problematic, and that Dave Duncan, the Cards’ pitching coach, excelled with just this type of player-one armed with good stuff, but who never seemed to put it all together. After a 2003 spent rehabbing the shoulder and rebuilding both his mechanics and his pitches, Carpenter exploded back onto the scene in 2004. The Cards would have been happy with that, but he took it up another notch in 2005, winning the Cy Young. The only downside was two years of heavy workload, including a 2006 campaign that went over 250 innings in return for a World Series ring. By 2007, Carpenter was broken again.

This time it was his elbow. Initially, the issue seemed minor, with surgeons scraping out bone spurs in his elbow, but just a few weeks after that, Carpenter’s elbow snapped during a minor league start. Now Carpenter needed Tommy John surgery, for the replacement of the ulnar collateral ligament. Bad, yes, but predictable. Pitchers routinely come back from the injury in a year, though the timing of Carpenter’s surgery would cost him most of the 2008 season. During his rehab, though, things have gone anything but predictably. He had a shoulder strain as well as nerve issues in his elbow (a common TJ complication) and in his shoulder, a combination which doctors have called “unprecedented.” The nerve transposition in his elbow is perhaps the most controversial element of what was done in Carpenter’s surgery; most surgeons currently move the ulnar nerve as a part of the Tommy John procedure to avoid this kind of setback, but it was not done in Carpenter’s case.

With that history, we can begin to understand what we’re looking for. Early in spring training, Carpenter is looking good, but his command is lacking. That’s a very typical situation, and in line with the few appearances he made last season in the minors. The general rule is that a pitcher with shoulder problems will exhibit a loss of velocity, while elbow problems are often first seen with a loss of control. It’s thought that this is related to proprioception, the ability of the body to sense where it is in space. (Close your eyes and hold your hand out. Turn the palm up. Move it to the side. See, you can do that because you have normal proprioception.) With Tommy John survivors, a common complaint is “my hand doesn’t feel connected to my arm.” It’s that way because it’s now connected in a different way, and the proprioceptive connections have to be rebuilt.

The bigger worry beyond command and control is how Carpenter recovers. The Cardinals have focused on him as a starter, but manager Tony La Russa has commented occasionally on the idea that Carpenter might now be better suited for the bullpen, where the team is deciding between a pair of rookies-hardly La Russa’s first choice, no matter how effectively they pitch-and Ryan Franklin for the role. Between his first two starts, Carpenter had no setbacks, did his side work, and showed no significant changes in style, velocity, or command when comparing the two outings. That’s a very positive sign, though it’s also very early in camp. Carpenter’s continued ability to recover is key. Though that’s true for any starter, it’s even more important for a pitcher with so many possible issues throughout his kinetic chain. If one part of the chain is weakened, it could lead to yet another breakdown.

That’s not to say that closing would work either. In moving to that role, Carpenter would be unlikely to go several days in a row, necessitating a “B” closer, though that role might be better suited for one of the rookies to gain experience in. La Russa and Duncan excel in their use of the pen, with their use of Troy Percival in 2007 being a case study for how they might handle Carpenter.

Carpenter’s arm is marked by scars in the same way some military uniforms mark the passage of time with stripes. The fact that he’s pitching at all is a reminder of just how far medical science has come in returning pitchers to the mound. Indeed, his right arm is perhaps the best single exhibit possible if Cooperstown decides to ever open a medical exhibit. Carpenter and the Cardinals just hope that he has one more comeback in him, making that exhibit wait.