Celtics trapped by the salary cap
The Celtics will be a luxury tax-paying team and therefore will have only the mini mid-level exception ($3 million) with which to attract anything more than a minimum-contract player. The Celtics are already over the salary cap with the team on the hook for $64.9 million for seven players (that's including a $5.7 million qualifying offer to Jeff Green, and that price tag should only rise). Boston will be able to sign its rookies and use Bird Rights to potentially pay to retain the likes of Green and Glen Davis.
After that? It's minimum contracts or bust.
Samuel Dalembert? Greg Oden? Tyson Chandler? Kwame Brown?
No. No. Heck no. Now you're talking! (And even Brown might get overpaid by another team).
That's not to say the Celtics can't get creative with the goal of bringing in another big contract. The team could work a sign-and-trade with Davis. Trouble there is that he's an unrestricted free agent and a team with deep pockets can sign him without the need to involve Boston (though it could be financially beneficial to Davis to go that route).
-- ESPN Boston