Playing against a pusher, I usually employ a method that Agassi described in his book Open: Make your opponent run. Hit from side to side, and mix it with some shots behind your opponent. In the 1999 French Open, against Carlos Moya, Agassi won the match with this method: Run, Moya, run.
You don't want to over-hit the balls and make errors. You don't try to paint the lines. You just take a commanding position, use good footwork, dictate where the next shot is going, and make your opponent run more and more.
You will feel tired from all the back and forth. But you must have confidence in this method because you know that your opponent is totally passive to your placement selections and he is much more tired than you are.
An all-court game with some chipping-and-charging and net finishes will help a lot, too.
Head Pro Tour 280 349g 7.6 pts HL / Razor Code 18 & Powergy 16 @55 lbs