The HR Derby Ruined Lee's Stroke?

It has been suggested by posters at Brewerfan.net and Carlos Lee himself that his poor production in the second half was a result of the HR Derby. The theory is that swinging for the fences for a few minutes caused Lee to change his swing. The pre and post all star splits is usually given as "proof":

                 AB  AVE  OBP  SLG  OPS
Pre-All Star    339 .268 .336 .528 .864 
Post-All Star   279 .262 .309 .437 .746

His slide actually began a full month before that, however:

                 AB  AVE  OBP  SLG  OPS
6/13 - 7/13      94 .213 .300 .426 .726

As I asked on brewerfan.net, doesn't the effect have to occur after the cause? Let's look at one final split:

                 AB  AVE  OBP  SLG  OPS
Before June 13  245 .290 .351 .567 .918
After June 13   373 .249 .307 .434 .741

Now, if we can just figure out what happened the morning of the 13th, the mystery will be solved! :)