Sawan, do you really want people to discuss how Sampras is much better than Federer. Because that's where this thread is going
I originally thought I would include Rafa in the discussion, but...I like broken records
Seriously though, I can imagine it would change some of the events...perhaps Rafa would even suffer. Don't forget: its not just who Roger or Rafa faces in the first round, but who his potential opponents face. Roger, Rafa, or Novak could have avoided a more difficult opponent because a player (say the #17 player in the world) knocked out someone they might find difficult.
ALSO...say Roger or Rafa had to face the #17 player in the world in the opening round. That could have an impact later down the line as far as fatigue, etc...so its not just an issue of upsets...but struggles down the line, as well.