World number two Rafael Nadal survived a first round scare at the Dubai Open before coming through 3-6 6-1 6-4 against unseeded German Philipp Kohlschreiber.

The Spaniard was twice within a point of going a break of serve down in the second set before clawing his way back to win in three.

Nadal got the first break of the match early but then lost five games in a row against the improving world number 27.

Kohlschreiber clinched the set after two dramatic Hawkeye challenges, reaching set point after the umpire over-ruled a line judge's 'out' decision, and Hawkeye showed the umpire to be in error.

Nadal looked in deep trouble early in the second set but saved a break point with an ace, and slowly gained the acsendancy after that.

He broke for 3-0 and 4-1 and broke again to win the set 6-1 - a slightly flattering scoreline after a closely-fought set.

In the decider the second seed broke for 3-2, immediately lost his advantage, then broke again in the seventh game and served out the match, as the German's resistance finally faltered.

Nadal was a relieved man after avoiding defeat.

"I was playing a big player. He's a top 30 player and one of the toughest pros on the tour, for sure," he said.

"It was a difficult match. I didn't play my best but it's not easy playing here, and I didn't come here with a great deal of confidence.

"This tournament gives you the toughest draw on the tour. But the good thing was I was one hundred per cent mentally.

"Maybe I didn't play my best but I was focused all the time and I was very happy with that."