Sampras would have taken that chump to school
I think you are selling Rafa short, it will be an incredible match for sure. Don't think Sampras ever faced someone who could hit as heavy as Rafa.
2011-19 Djokovic.
2014-19 Federer.
Not sure about the second one, Federer really hasn't performed well at the open since 2010-11. With exception of 2015.
And I have my doubts about how much 2015 will be able to do against a Nadal who will win free points on serve and expose his net rushes from the back of the court.
I believe an exceptionally solid aggressive baseline player will have the chance of winning . That's why I chose 2006 Federer and 2011 Djokovic.
Del potro in his 2009 F form might stand a chance as well.
From my time of watching, I can only think of
2 -3 year winners who could really pose a challenge to Rafa.
A testament to the hard work Nadal put in to win his first HC slam.