I actually hadn't thought of dealing Payton for Shareef. From Peter May in the Globe:
Meanwhile, here's something to think about regarding our newest arrivals, Payton and Rick Fox. They are both valued in large part because of their expiring contracts (Fox more than Payton in this instance because he may not be playing at all and insurance might kick in with some coverage). In other words, the ex-Lakers are assets as much as they are players. Those two and Yogi Stewart could be packaged in February for, say, Shareef Abdur-Rahim, a player Ainge has angled for in the past. Or for others in a salary dump. But as I wrote yesterday, it's hard to envision Payton being anything other than miserable here; he wants a ring and time is running out. And the last thing Doc Rivers needs on this young team is an unhappy Gary Payton, which is why he and Ainge were in Los Angeles Friday trying to state the case. Especially when you had a stand-up guy like Chucky Atkins around
I'm not sure we'd bother making a trip to L.A. to talk to him and convince him to be excited about Celtics basketball if we were just going to flip him to Portland. I'm sure if Portland was involved, we would have just done it directly with a 3 way trade, rather than let Shareef stew for another 2 months.