Actually he is pretty good at starting. Is it playing with better players or that he plays better playing more minutes or what, but he definitely is not a bad starter. He isn't top 15 starters in the league good but his numbers are much better than when he comes off the bench.
226 non starts 18 mpg 6.7/3.3/2.0 on 37.1/34.4/77.8 with 48.7 TS%.
26 starts in 32 mpg 14.7/6.0/5.7 on 39.9/39.6/80.7 with 52.7 TS%
Starting in last year's playoffs 19 starts 36mpg 16.5/5.3/5.7 on 40.6/34.7/82.1 on 53.7% TS%.
That said, I think shrinking the roster and sitting Rozier might be best thing for this team right now. He has been horrendous.
I would say he's about replacement level as a starter. His scoring efficiency is just OK, he's not a very good playmaker, his court vision is straight up bad, and his defense is inconsistent.
As we've covered, as a reserve he's awful.
We also know he's been one of the players in the locker room who is most noticeably dissatisfied with his role.
So my question is, why wasn't he traded at the deadline or earlier?
Keeping him has only resulted in his value tanking, and his play has hurt the team. Failing to trade Rozier sooner is a pretty significant mistake by Ainge and crew, I would say.
It may be that the market for him wasn't very strong, even before his effectiveness on the court took a turn for the worse. But I think it's been apparent for a while that it would be addition by subtraction.