A wasteful Rafael Nadal survived another slight scare at the US Open, overcoming Leonardo Mayer in four sets in the third round on Saturday.

The world number one squandered his first 13 break-point chances before settling to secure a 6-7 (3-7) 6-3 6-1 6-4 win over Mayer under the roof on Arthur Ashe Stadium.

Nadal eventually needed three hours, 15 minutes to claim his victory, having converted six of 25 break points to reach the last 16.

Awaiting the 15-time grand slam champion, who also struggled early against Taro Daniel in his previous match, in the fourth round is Ukrainian Alexandr Dolgopolov.

Nadal had won his previous three meetings against Mayer, a lucky loser, without dropping a set, but he let chances slip to fall behind.

However, once the Spaniard took an opportunity, he settled, and Mayer rarely troubled him on his serve.

Early missed opportunities proved costly for Nadal in the first set, as he failed to take any of the six break-point chances Mayer presented him across the fourth and sixth games.

The Argentinian grew in confidence as the set wore on, holding to love to force a tie-break when Nadal netted a backhand.

And the world number 59 sustained that momentum in the breaker, Nadal sending a forehand long to hand his opponent the opener.

In huge trouble, Nadal saved two break points in the fourth game of the second set, before he continued to miss chances to allow Mayer to hold for 3-2.

But finally, Nadal converted his 14th break point – Mayer sending a forehand wide to see the Spaniard go 4-3 up.

That proved to be a huge moment as Nadal, relieved having finally grabbed an opportunity, closed out the second set and raced out to a 3-0 lead in the third.

It was cruise control for Nadal from then on, the two-time champion in New York finding some much better form as he booked his spot in the fourth round.

STATISTICAL BREAKDOWN
Nadal [1] bt Mayer 6-7 [3-7] 6-3 6-1 6-4

WINNERS/UNFORCED ERRORS
Nadal - 39/26
Mayer - 45/52

ACES/DOUBLE FAULTS
Nadal - 4/3
Mayer - 12/5

BREAK POINTS WON
Nadal - 6/25
Mayer - 1/3

FIRST SERVE PERCENTAGE
Nadal - 68
Mayer - 63

PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Nadal - 73/69
Mayer - 60/57

TOTAL POINTS
Nadal - 140
Mayer - 120