Agree,it's the pressure he can't handle anymore it seems
When he plays a Tsonga for example, he knows he doesn't have to force his 1st serve because Tsonga's ROS sucks so obviously, his 1st serve percentage is much higher.
It's obviously not the case against a returner of the caliber of Murray.
True. In 2008 it was good. After working with Todd Marting it became a mess, in 2009 he was doublefaulting like Kournikova. It got better after, but it was barely decent. Even last year.
I remember that in the 1st set of the USO 2007 Final at something like 4-4 Federer had only got 4 points on Djokovic's serve (of course, Nole went on to lose a bunch more to choke that set), nowadays he loses this amount in one or two service games.