He is an underrated player, very talented, Celtics should sign for the rest of the season.With a team option for a second year. His agent might say no, but I'd try to lock him up for a second year. That would give us early bird rights.
One thing Ainge could do, if there's enough room, is use a portion of the bi-annual exception on Terrence (an exception I don't think we'll end up using next year), which may allow us to give Williams more money this year, and at the same time secure him in contract for next year.
I think that would be a waste of money. Williams is a minimum-level player right now, and there's no need to limit potential flexibility next season.
I'd sacrifice that flexibility for someone who'll be an expiring contract next year, plus will make some of our bigger contracts in our guard rotation expendable to be used to try and trade for a bigger fish.
We're very limited in the additional money we can waste this year, so don't see much of an issue.
The important consideration for me is, what are the projections for next year Salary Cap, and how far along are we under the Apron so that we can fit a full mid-level player, and make decisions based on that.
But also remember, that if you think you have a good opportunity for a sign and trade, just for kicks say Al Jefferson, then that means you can't use the full MLE exception, so you're better off having someone like Terrence in the roster, at relatively very low money, and turning your expendable players into more value if the opportunity presents itself.