Okay, I criticized Cooper below and really didn't give any suggestions on what should be done... so Here it goes.
If you want to shake up a lineup, you don't screw around with the only part of the lineup producing as expected... Bourn has been a terrible lead off hitter this year with an OBP of .310. Move Towles to lead off. He has some pop, and so far this season is sporting a .395 OBP. Right now he's hitting a little like some guy named Biggio used to do... I seem to remember Biggio being a pretty decent lead off hitter. Don't get me wrong, I'm not saying Towles is the next Biggio by any means... but so far he's producing like a decent lead off hitter. Move Bourn back to 8th in the lineup.
I can't really say much about Matsui.. he's a career .325 OBP guy which doesn't suit me as a lead off hitter... he can stay at 2nd for now and see how he turns out. Lance, Lee and Tejada should stay where they are. Lee hasn't been outstanding this season(low OBP), but he'll come around. Pence has been terrible this year, but has shown some life by batting 6th... stick him there for now. Your 7th hitter is trash regardless who it is for now... Loretta/Blum, neither are doing anything of worth... but we don't have much else until Wigginton gets back. Slot that guy 7th for now. So here is my lineup if I'm going to be making changes.