It's not like he didn't see the court again after his injury. Look at his game log:
http://sports.yahoo.com/nba/players/3764/gamelog;_ylt=Aumj0BgnxVwH3rNAA1ya0WXqPKB4
He came back in early February. The most minutes per game he averaged all season was February. That was probably his best month all season, truth be told; he starting losing playing time as March rolled around, as his play started tailing off (and Tony's play started to improve).
But, Quis was fine, immediately post-injury. He went into a slump (it happens to everyone), and Tony's good play didn't really leave much of a chance for him to work his way out of it.
Thanks, Bird. I posted a reference to the game logs above, but apparently the notion that Quisy lost his spot due to injury persists.
One correction, though: Pierce was out for a bit in February as well, so there was some time for Quisy and also some cause for his scoring to be a bit higher...temporarily...
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I do tend to agree with the notion that the utility role diminished his production. Perhaps playing strictly on the wing (no PG duties) will help, as will having a good handler and scorer like Nate on the court with him. Nate/Quisy have the potential to complement each other well, though we didn't get much of a chance to see that combo last season.