I don't understand how signing a guy to a 10day contract means Green is gone.
Especially given that they play different positions.
Williams is good enough to start from a pure talent pov, but he has a long way to good to prove he's got the head to do it. In fact, he would be a great backup 2/3, but again he's got to show maturity and discipline that he has never shown in the NBA before.
Potentially, he could back up Pierce and Lee allowing Green play all his minutes at the 4. Bass becomes more expendable if that happens. Highly unlikely unless he's changed a lot since he was last in the NBA, though.
Bradley/Lee/Williams/Green/KG is potentially a *great* defensive unit that would have to run, run, run offensively.