Here's what I hear about Walker. He's looking very good right now but in the past he's been not so good and he's expected to go through some rough patches. Also Alou has said that with Schmidt back, Fasserro will split save opps with Walker to keep him from being overworked. You already have 3 awesome closers... but at the same time, you have a nice crop of outfielders too. I can't believe you've got Pods on the bench. You must be running away with the steals category. If you need power numbers though, grab Mench. If you're behind on saves grab Walker... but sell high on him if you can. Personally I would grab Walker because if you don't someone else in your league will.
In either case, drop Encarnacion. No one else will grab him, if Mench is still floating he'll float as well. You should be playing Pods anyway.
Hope I was some help to you. See mine if you have a sec, the link's in my siggie.