It appears that Roger Federer has not been up to par since his emotinal reaction to his loss to Rafael Nadal.
Some sport psychologists believe that a display of emotions is a good thing for some athletes. Other mental toughness coaches may feel that wearing one's emotions on one's sleeve can be disruptive to one's game.
Federer may not be comfortable with letting it all out. Perhaps he, like Bjorn Borg, plays best when he keeps a lid on his feelings. Time will tell what will work best for him at this stage of his career. Clearly, Nadal is still the player that seems to upset him the most at this point in time.
The psychological aspects of tennis are discussed in my book Zone Tennis which is available at www.amazon.com and www.barnesandnoble.com.
Here is a link to get your copy.