What scoring format is your league using? How many teams are in your league? What's your team look like?
I think under any circumstances, a Gasol for Ridnour trade would be unwise, especially with the position battle Ridnour is in with Watson. However, you're not going to get a 20 and 10 guy for an injured Pau.
If your league allows daily roster changes, I would just let Pau sit on the bench and stream a roster spot if there's a decent amount of good players on the waiver wire. If your team is strong enough hold on and at least stay in playoff contention, then Pau might put your team over the top upon his return. If you don't have good enough players, then whether you sit on Pau will make or break your season.
You might be able to get a 14 and 8 guy for Pau if you think you need to trade him.