Didn't see the match, but everyone has a bad day. What is not normal is one single guy dominating every other contender day in and day out, as Djoker did in 2011 or Fed in 2006.
All top 100 guys are incredibly talented and dedicated, they devote their lives to beat their peers. One-sided, continued dominance should be the exception, not the rule. That's what makes Federer's run, or Nole's, or Nadal's on clay all the more incredible and special.
Fan of the fans.