Rafael Nadal has revealed that his US Open clash with Diego Schwartzman was tougher than the result suggests.

The world number eight progressed to the third round with a win in straight sets, but Nadal was broken twice by his opponent in the first set, before eventually taking the tie-break.

Speaking to ESPN after the match, Nadal said: "That first set was very important, with these humid conditions I think that I was playing very aggressive, playing at a very high level so that first set was very important for me.

"I felt a little bit more comfortable [in the second set], I think I started the match playing well with good feelings.

"Then you have to fight - the second set had been tough but I was able to break back quick and then have two breaks."

Nadal will take on Fabio Fognini in the third round on Friday.