There are the big-names, like Elton Brand and Ben Gordon, who could opt-out this year to hit the market. Or genuine free-agent players like Gilbert Arenas, who will command big money. The Celtics aren't players for these gentlemen, not only due to their prohibitive cost and the Celtics' lack of cap space, but that these men start at positions the Celtics have filled.
So let me throw another name out. One you may know fleetingly. Beno Udrih from Sacramento.
The Celtics one real weakness is a reliable backup point guard. Udrih could fill that role easily, maintaining a high level of competence on the floor for Boston. His average for the 07-08 season was 12.8 ppg, 4.3 apg and almost one steal. Those numbers are comparable to Rondo's, with Beno actually averaging more points. If (God forbid and I am knocking on wood right now) Rondo got hurt, Udrih could easily step in to run the floor as a starter.
Most acceptable is this: Beno made a little more than a half-million last year. The Celtics could use their mid-level cap exception (around 5 mil) to make a highly competitive offer. Combine that with the chance for him to come to the current NBA Champions, a team with a very good chance to repeat, and I think the Celtics could grab him.
It's a modest move in the free-agent market, but one that could pay off huge next year.