<div><p>AUCKLAND (Reuters) - Big-serving American John Isner advanced to the Auckland Open semi-finals for the first time with a three-set victory over top seed Tommy Robredo on Thursday.</p><p>The 24-year-old Isner, who was knocked out at the quarter-final stage last year, overpowered the 16th ranked Robredo with 20 aces to run out a 7-6 3-6 6-4 winner.</p><p>"It was tough... and I certainly had to dig deep," the popular Isner told reporters of his third three-set victory this week. "Down a break in the first. Down a break in the third. I had to play pretty well to keep my head and that's what I did."</p><p>A noticeably frustrated Robredo said that while he had broken Isner's booming serve three times, he still had trouble with a ball that was clocked moving at more than 220 kilometers per hour (137mph).</p><p>Robredo, who helped Spain to Hopman Cup victory last week, said he was nevertheless pleased with his form heading into next week's Australian Open.</p><p>"I feel good. I'm not going to change much from the way I played or am feeling," Robredo said.</p><p>"I played great from the baseline, was returning great and only had a couple of mistakes with my serve. The rest is positive for me, even though I lost, but if you play a guy like John, it can happen."</p><p>Robredo's demise ensured that none of the top four seeds would be in the semi-finals on Friday.</p><p>Isner will now meet Spain's Albert Montanes in the semi-finals after the eighth seed beat Swiss qualifier Michael Lammer 6-3 6-3.</p><p>By making light work of the 209th-ranked Lammer, Montanes has advanced to the semi-finals without having to beat anybody ranked in the top 200 in the world.</p><p>Isner said he doubted if the ease of the Spaniard's path would have any bearing on their match.</p><p>"He has a deceptively strong serve," Isner, who beat Montanes in Auckland last year, added. "He's also very fast and has some great groundstrokes... so it will be tough."</p><p>France's Arnaud Clement continued a strong run with a 6-2 7-5 victory over sixth-seeded Austrian Juergen Melzer and will meet 2008 champion Philipp Kohlschreiber, who beat France's Marc Gicquel 6-3 6-1 in the late match, in the final four.</p><p>(Editing by John O'Brien)</p><img src="http://admatch-syndication.mochila.com/images/ad.gif?aid=66879120&bid=informcom" /></div><div id="copyright"><div>

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