Top seed Lleyton Hewitt [Images] breezed through to the last four of the Tennis Channel Open on Friday with a 6-2, 6-0 win over Germany's [Images] Philip Kohlschrieber.

But third seed Tommy Robredo was ousted 7-6, 6-4 by big-serving Croat Ivo Karlovic on a cold, windy day.

The tournament lost another player to injury, Belgium's Xavier Malisse retiring with an Achilles injury when he was down 6-2, 2-0 to American Paul Goldstein.

Malisse joined Andy Roddick [Images], Germany's Tommy Haas and second seed Nicolas Kiefer among those how have pulled out or retired.

Hewitt, who will play Goldstein in the semi-finals, played a smart, conservative contest against Kohlschrieber who couldn't get to grips with the conditions.

"It's a matter of focusing on what you have to do," Hewitt said. "There's balls going everywhere and papers were flying round. The person who is able to keep his focus will win the match."

Kohlschrieber upset Hewitt earlier this year at Adelaide, but had trouble finding his rhythm on Friday.

"The biggest thing in the wind is to keep your game compact and not give cheap errors," Hewitt said.

"You need a high first serve percentage, but you are going to get double faults. It's a matter of not getting negative and playing the percentages."

Spain's Robredo was equally frustrated with the conditions, as well as with Karlovic's service bombs.

"I was lucky, but in the wind you have to be lucky," Karlovic said. "With the wind, it's hard to play to my potential."

Karlovic will face the winner of fifth seed James Blake and Dane Kenneth Carlsen.

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