Andy Murray teetered on the brink before beating Alexander Zverev in a marathon that lasted more than three hours on Wednesday to reach the quarter-finals of the Qatar Open.

Murray won 7-6 (7/5), 2-6, 7-5 after he was twice two points from defeat on his serve in the third set.

In his on-court interview after the victory, Murray said the crowd helped him.

"It makes a big difference for the players when we come and get a lot of energy and a great atmosphere from the crowd," Murray said. "I obviously enjoyed playing in that atmosphere tonight."

The British former World No. 1, will face French qualifier Alexandre Muller, who upset Dutch eighth seed Botic van de Zandschulp 6-2, 6-4.

Murray and Muller have never met.

"Not so familiar," said Murray. "But he's obviously had a good week this week coming through qualifying. He will have played four matches now, so obviously likes these conditions,"

"My coach will obviously watch video and stuff tonight to get a bit more familiar with his game, but it's an opportunity for me in the quarters tomorrow."

Top-seeded Andrey Rublev, the Doha winner in 2020, was in danger of suffering a fourth opening-match exit in five tournaments this year before fighting his way back from 2-5 in the third set to edge Dutchman Tallon Griekspoor 1-6, 6-1, 7-6 (8/6).

Griekspoor squandered three match points on his serve in the ninth game of the third set.

He then saved two match points in the tie-break before Rublev won in one hour 54 minutes.

Rublev will face Jiri Lehecka, a 21-year-old Czech, who beat Finn Emil Ruusuvuori, 6-2, 7-6 (7-2).

Canadian second seed Felix Auger-Aliassime struggled against Jason Kubler's serve in the first set but recovered to overcome the Australian  4-6, 6-1, 6-4 after two hours and 16 minutes.

Kubler had won the only previous meeting in Newport last year.

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