I don't like Battier much, but even I wouldn't do that trade. Now, if Stojakovic was free... nope, still wouldn't do it!
There will be less minutes at the 3 availiable, so with the downward trend in point and less time, I'd say maybe 8 pts a game. And OP said it would be Battier+Jeffries for Peja, so I would think Jeffries stats would need to factor in somehow. It's a bad idea before and after stats analysis.