Del Potro played for two days in a row and the match went for over four hours and is officially the longest match of this Wimbledon. Besides , Del Potro was obviously frustrated at various points in the match. While I don't think Del Potro would be physically wasted, I expect him to be mentally wasted. You need 4 or 5 sessions with a Psychiatrist after playing a match with Simon to recover from it.
Del Potro made 63 UFE over the course of four sets in that match. Moreover, he was broken more times by Simon than the other way around, even though he won.
Del Potro's backhand is always a question and will be more exposed with Rafa's high bouncing top spin shots.
At the beginning of this tourney, when I looked at the draw, I thought that even if Rafa does not go out in the third round to Mischa (who did not even make it there), he will definitely be taken out by JMDP in QF. I no longer believe so.
But, Rafa is not playing great either and is already broken four times. Hence, I would give the gentle giant one set.
The match will be over in under three hours though.