Say ahh.

Semih Erden, the Turkish Shaggy, continues to battle through a shoulder injury that should require surgery at some point (likely after the season). But Doc Rivers isn’t convinced Erden will be able to play through the pain all year. (Boston Globe)

“There’s going to be a point when Semih can’t play,’’ Rivers said. “I don’t know that, but I believe that. I just think that with the shoulders, there’s a point where it’s going to come out and then he’s not going to be able to play.’’

Erden shows a nice basketball IQ when he’s on the court. He positions himself well (for the most part), and has been one of the rare rookies to see the light of day in Rivers’s rotation.

He has also been, according to PER, one of the league’s worst players. In fact, Ryan Degama of Celtics Hub believes it might be time to offer Luke Harangody some run. Any time a person who knows things suggests Harangody might be a solution, the problem must be a pretty big one.

Erden shows flashes of potential, and a seven-footer with good mobility and a solid knowledge of the game should be useful. But he hasn’t been effective yet. Not at all. So far this season, Erden has a negative-46 plus/minus — for a 12-4 team that sits atop the Eastern Conference. That’s not good. Erden’s putrid PER (6.88) suggests that his plus/minus isn’t just an effect of playing minutes with poor teammates. He deserves a lot of the blame himself.

Seeing that Erden is — by a few advanced measures — the Celtics’ worst rotation player, losing him to injury for a period of time shouldn’t be the worst thing in the world. Then again, if Jermaine O’Neal stays hurt (and he might), Erden isn’t just the Celtics’ best option at backup center — he’s also the only option. Glen Davis can fill in at center occasionally, but he’s also the only reliable backup power forward.

I like Erden’s game. I really do. I think he’s going to help down the road, and I think he’ll help this season. He just hasn’t helped much yet. Maybe that’s because his shoulder is limiting him, maybe it’s because the transition to the NBA is difficult, or maybe it’s because he just isn’t ready.