(Reuters) - Top seed John Isner narrowly avoided a second straight first round exit as the big serving American edged past Canadian Jessie Levine 7-6 5-7 6-4 at the Delray Beach International on Tuesday.

American Isner was tripped up in the opening round of last week's Memphis International by Uzbek Denis Istomin and the world number 15 again found himself in trouble on the hard courts.

John Isner of the U.S. hits a return to Brazil's Thomaz Bellucci during their Davis Cup world group first round tennis match in Jacksonville, Florida February 3, 2013. REUTERS/Daron Dean

This time, however, the 6-foot-9 inch (206 centimetres) Isner was able to blast 28 aces en route to victory in an opening match that lasted over two hours.

All seemed to be going to plan as Isner seized the critical first set in a tie-breaker 7-3 but he had his service broken en route to dropping the second set, forcing a decider.

But the American, who has been plagued by knee trouble, held firm in the third to advance, much to his relief.

"Jesse's good. I've always had trouble with him. Honestly, it was a good one to get through," Isner told the ATP website.

"A win is a win and I haven't had many lately. I'm just trying to get this train going. I'll rest up and I anticipate I'll be better."

Another big server, Croatia's Ivo Karlovic, also advanced at the hands of Memphis winner Kei Nishikori. The Japanese forced to retire at 5-4 down in the first set with a stomach muscle problem.

Second seed Tommy Haas was another winner but the German was in no celebratory mood.

Haas and Igor Sijsling were locked at one set all when the Dutch player quit with an ankle injury after the second set.

In the final game that Sijsling lost he blasted three balls into the stands, one hitting a spectator and drawing a code violation warning.

"What a strange match. You never want to win a match like that," Haas told reporters. "It's not a proud win for me."

(Writing by Jahmal Corner in Los Angeles. Editing by Patrick Johnston)

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