A big issue with Rivers is he's been behind Evans,Gordan,Holiday all of last season. It's hard to get playing time and constancy with that.
The last 5 games he averaged 14ppg when he got more that 30 min. Couple games he shot 33%, but I think there is some game there.
IF AB is gone, I could see DA making a move. He did run some point, and would be a much bigger guard than Pressey.
Rondo/Smart/Rivers/Young would be an interesting back court.