It's not likely a move made to keep him, but rather give the team a chance to make a trade for Cassel.
Some quarterback-needy team will likely make a move on Cassel. If the Patriots did not put the franchise tag on him, Cassel could have left without any compensation.
Now it will cost draft picks.
Or the Patriots can simply keep Cassel as insurance in case Tom Brady isn't ready for the open of the 2009 season as he recovers from major knee surgery.
That is unlikely. Cassel would count $14.6 million against the cap. With the news that Brady is making progress in his recovery, this looks more like a team trying to get something of value for Cassel.
What's a fair price?
Cassel could be a one-hit wonder, so it's tricky. That's the concern for any team trading for him. Rushing to judgment on quarterbacks is risky -- see David Garrard and Derek Anderson -- and in this case you'd have to give up picks and give Cassel a long-term deal.
Is he worth that? He played well last season, his first as a starter since high school, but he struggled with the deep passes.
That would be a bit of a red flag for me.
I've I developed Cassel I'd keep him and feel good about playing him. But trading and paying him will is a big risk. Somebody will take it. I'm not sure I would.