Detach the name from the performance and just call him Player X.
In 2011, he was limited to 99 games, but when he played, he was an above-average performer relative to others at his position, hitting .276, with an .823 OPS.
In 2012, those numbers dipped slightly, as he continued to battle more injuries; Player X had a .783 OPS, while seeing a predictable regression in his defense.
Because of offseason surgery, Player X was limited to 44 games in 2013 -- and he showed some pop. His OPS slid only slightly, to .771, although the questions about his ability to play regularly in the field continued to grow.
Player X is 38 years old, and as he deals with a condition that can be degenerative, he has missed 221 games the past three seasons. When he plays, he is still an above-average-to-average offensive player, compared to others at his position. In the small sample of games he played in the field in 2013, one defensive metric has him as average.
In short, the pure performance evaluation would be: Player X can be a productive player, although there are significant questions about whether he will be healthy enough to be counted on.
There is more to the equation than baseball production, however. So much more.