(REUTERS) - World No. 1 Rafael Nadal came from behind to dispatch underdog Taro Daniel of Japan 4-6, 6-3, 6-2, 6-2 in front of a sold-out crowd at the US Open on Thursday (Aug 31).

Despite playing a marathon five-setter the day before, 121st-ranked Daniel looked the fresher of the pair at the outset of the match, breaking Nadal to take a 5-4 advantage when the Spaniard dumped a forehand into the net.

He eventually won the set and appeared poised to deliver a massive upset.

But Nadal soon found the accuracy that had eluded him in the first set and his booming serve proved too much for the exhausted 24-year-old, who is now 0-6 against top-20 opponents in his career.

"All the matches are difficult, especially here where everyone wants to play their best," Nadal said in an on-court interview at the Arthur Ashe Stadium after the win.

"It's true that I didn't play very well tonight but it's also true that I'm through to the next round."

Nadal is now one step closer to a potential semi-final match against third seed Roger Federer, who won his second consecutive five-set match earlier on Thursday.

"I am here to improve every day. I believe I can do it much better and I really feel I am going to do it much better," Nadal added.

Next up for the 31-year-old is a third-round match against aggressive Argentinian Leonardo Mayer.