Rafael Nadal overcame a first set wobble for the third match running at the US Open before eventually conquering Argentine Leonardo Mayer in four sets.

Nadal, the world number one, is the bookmakers favourite to win the title in New York, however, there were signs in his 6-7 (3-7) 6-3 6-1 6-4 victory that the fiery Spaniard is more than beatable.

Mayer, who lost in the final round of qualifying but was handed a place in the main draw as a lucky loser, played some inspired tennis for a set and a half, yet Nadal lacked the sparkle that saw him claim an unprecedented tenth French Open crown back in June.

At one stage in the second set, the Spaniard had failed to convert any of his 14 break points, with his returns regularly letting him down in big moments.

Eventually, though, Nadal’s resolve and persistence hurled him over the finishing line on the Arthur Ashe Stadium, and once he nudged his nose in front there was little hope for the 30-year-old Argentine.

In many ways, this was similar to Nadal’s second round match against Japan’s Taro Daniel, who also had the top seed on the ropes before eventually running out of gas.

A higher ranked opponent may not be so lenient, though, and Nadal will need to rediscover his ruthless demeanor if he is to win the trophy in a week’s time.

Next up, in the fourth round, is the unorthodox Alexandr Dolgopolov from Ukraine, who defeated Viktor Troicki in straight sets.

Stuttering start from Nadal

Nadal made a tentative start against Mayer, serving two double faults in the opening game before holding his delivery.

Mayer, who hadn’t taken a set off Nadal in three previous meetings, had his credentials examined in the fourth game, when he fended off four break points - two with aces.

The Spaniard continued to turn the screw, however, he was unable to convert any of his six break points in the opening set.

That allowed Mayer to grow in confidence, and the Argentine regularly went toe-to-toe with Nadal from the baseline.

Even the 30-year-old’s single handed backhand was holding up against Nadal’s heavy topspin forehand, which misfired several times in the first half of the match.

Mayer didn’t see any break points in the opening set but was the better player in the breaker, which he won by seven points to three.

Break point finally converted

There were opportunities for Mayer to breach the Nadal serve at the start of the second. However, with support from the Arthur Ashe crowd, the bullish Spaniard held on.

The key moment came at 3-3, when Nadal finally converted his 15th break point after Mayer skewed a forehand into the tramlines.

From there, Nadal won the next five games to level the match and take a 3-0 lead in the third.

An early break in the fourth eased some more pressure, and the Spaniard continued to flick through the gears without hitting top speed, closing out the match in three hours and 15 minutes.

No problems for Federer

In a delayed night session, Roger Federer made lighter work of Spaniard Feliciano Lopez.

The Swiss had been taken to five sets in his opening two matches but came through 6-3 6-3 7-5 in an hour and 46 minutes.

Federer will now face German Philipp Kohlschreiber in the fourth round.

"I'm really excited how I feel after two five-setters," said the third seed after the match.

"It was clearly nice to go up two sets to love for a change. Feels different from there."