Robredo falls to giant Isner

American John Isner claimed the scalp of top seed Tommy Robredo to progress to the semi-finals of the Heineken Open in Auckland.

Isner survived a gruelling three-setter to advance with a 7-6 (7-5) 3-6 6-4 triumph.

"I was happy how well I hung in there [after] being a break down in both the first and third sets," said 6ft 9in Isner, who struck 20 aces in the encounter.

"I felt I served pretty well today. The outdoor hard courts suit my game; the balls bounce higher and I can play aggressively."

He will now face eighth seed Albert Montanes, who claimed a place in his first hard-court semi-final with a 6-3 6-3 win over Swiss qualifier Michael Lammer.

"It was a very tough, well-fought match," said Montanes.

"He was making me move a lot and I am happy that I played a good match from the baseline. It is great to reach my first semi-final on hard courts."

The second semi will be between Germany's Philipp Kohlschreiber and Frenchman Arnaud Clement.

Kohlschreiber beat France's Marc Giquel 6-3 6-1 while Clement saw off sixth seed Jurgen Melzer 6-2 7-5.