Nadal's Wrist Tape

Seems he has wrist troubles, based on the commentators before the 1st rain delay.
I doubt it considering that the tape doesn't actually cover his wrists at all.

James Blake seemed to think that it was to prevent sweat from running onto his hands. The weather was particularly humid and Nadal already sweats a lot. Schwartzman asked for sawdust, so I'm inclined to believe it's a sweat thing.