I've seen Shavlik play since he was in high school. UNC/Duke went through an intense recruiting battle and he ultimately chose Duke.
Like a previous poster said, he was very underwhelming at Duke (He was by far the best player in the state of NC, and one of the best in the country, going into school). He was considered one of the biggest recruiting busts ever in College basketball history.
He left school early, which left everyone scratching their heads. Predictably he went undrafted. He just isn't skilled enough to contribute on this level, or even on the College level.
Celtics fans should hope he gets little to no playing time. DJ White will be MUCH more valuable to this team.
Shavlik's biggest claim to fame is his quote from an article about potentially playing with gay players (after Amechi had come out saying he was a homosexual), "as long as you don't bring your gayness on me."