World No.1 Rafael Nadal showed his trademark grit and determination on Thursday as he reached the semi-finals of the Qatar Open with a 7-5 6-4 victory over Latvian Ernests Gulbis.

The Spaniard has never previously won an ATP World Tour title in the first week of the season, but he is on course to do so this time after seeing off Gulbis, the only other seeded player left in the draw.

Gulbis hit some startling winners, led 5-4 in the first set, and had three points to take a 4-1 lead in the second, but Nadal was always tough and resilient when it mattered most.

Nadal also served very well, approached the net more than usual, and his standard went up markedly when it seemed that Gulbis might take a grip on the second set.

“I am not thinking about Australia,” he said, referring to the first grand slam event of the year, starting later this month in Melbourne.

“I am thinking about Doha.

“For me this is a tournament I like to play but have never had a chance to win. I’m trying to be competitive, and after the match I am hoping I will feel competitive for tomorrow (Friday).”

Uncharacteristically teeming rain caused a two-hour delay to proceedings, before a further interruption of 10 minutes during which the two players sat on court with towels over their heads.

That did not seem to disrupt Gulbis’s rhythm, for he continued to hit spectacular winners, only to attempt a risky drop shot at 30-40 in the 11th game which effectively cost him the first set when it landed wide.

Gulbis then played beautifully for the first five games of the second set, dragging the match to another dimension.

He broke his opponent in the second game, only for Nadal to break back in the fifth game thanks to his formidable forehand.

He then broke again, decisively, in the seventh game and saw out victory with a backhand pass struck from well behind the baseline and which touched the net on the way over.

“That was a very good sign,” said Nadal.

“I have been practising more than I usually do for a tournament, but I understand that that is what I need to do.”

He next plays unheralded German Peter Gojowczyk, who earlier saw off compatriot Dustin Brown 6-3 3-6 7-6 (7-5).

Later, a second German made the semis when Florian Mayer, the conqueror of Wimbledon champion Andy Murray, missed four match points in the second set against Victor Hanescu of Romania before winning 6-4 6-7 (8-10) 6-4.

Mayer will face Gael Monfils in the last four after the Frenchman defeated Daniel Brands 6-2 6-1.