What are you talking about, almost all of his French Open titles prior to Djokovic becoming a force on Clay have been cakewalk draws, almost no clay court specialists and easy players to beat, as good as Rafa is on clay, he had a pretty poor competition on Clay then, unless you count Federer hard opposition on Clay which is his worst surface and was a good matchup for Nadal on Clay.
US open 2010 cakewalk draw and exhausted Djokovic in the final, can you say that was a hard draw?
Honestly people focus too much on rankings, someone in form can be a much dangerous opponent than someone who is a higher rank but out of form, Nadal faced unranked players before who were dangerous and in form, he also faced very high and top 10 players who were out of form, how do you define whats the easiest match?
He beat at least one of Fraud/Djok in 8/10 RGs. Clay might not be their best surface, but they're ATGs and are good on all surfaces. They are the 3rd and 2nd best claycourters of the last 15 years. For example, Coria is considered a very talented claycourter, yet he was 0-2 vs Fraud on the dirt.
His draws until the final at USO 10 and USO 13 weren't particulaty difficult, but he still had to beat Djokovic who was #3 in 2010 and #1 in 2013 and his most difficult matchup on hardcourts. And I don't think Djok was tired, those 5 setters were not particulary long, not to mention the final was postponed a day because of rain.