Grigor Dimitrov is World No 16

#0: Play a down-the-line backhand (to a right-hander's forehand). This often forces an opponent to change his attack to a cross-court shot, which goes to your forehand. This is what Federer changed early in his career after he lost to Hewitt and Agassi a few times.

They both had better backhands, so Roger kept playing a cross-court backhand (since, in theory, this is a better way to defend), but he never got out of the cross-court rally. He then learned to play an occasional down-the-line sliced backhand and, in most cases, received a cross-court shot to his forehand, with which he immediately attacked.

http://www.youtube.com/watch?feature=player_embedded&v=ubmmOPuuGYc

Note the relentless play of Hewitt to Federer's backhand and all the different tactics Roger tries to get out of that - changing pace, spin, playing down the line, moving around to play the forehand, etc.