New American No. 1 Mardy Fish faltered on home soil as Japan's Kei Nishikori dumped him out of the US Men's Clay Court Championship quarter-finals in straight sets.

13092 - Fish flops in Houston quarters

Nishikori completely outplayed the top seed in Houston, earning three breaks and conceding just 10 points on serve all match as he won 6-3 6-2.

In the semi-finals he will meet Pavlo Cuevas, who also created an upset by ousting third seed Guillermo Garcia-Lopez 1-6 7-6 6-3.

And No. 4 seed John Isner also went out, losing an amazing serve-fest 7-6 6-7 7-6 to Ivo Karlovic. Standing at a combined 413cm, the two giants shared 47 aces in their three-hour marathon. Ryan Sweeting came back to beat Teymuraz Gabashvili 3-6 6-3 6-1 in Friday's other quarter.

Elsewhere, Gilles Simon was dumped out of the Trophee Hassan II in Morocco by Italian Potito Starace - who booked his place in the semi-finals with a 6-4 3-6 6-4 victory.

Top seed Albert Montanes avoided a similar exit, seeing off another Italian, Fabio Fognini, in straight sets 7-6(1) 6-1.

Montanes will now face fellow Spaniard Pablo Andujar, who eased past Pere Riba 6-2 6-2, in the semi-finals - while Starace will face eighth seed Victor Hanescu. Hanescu, who made the final of this tournament last season, beat qualifier Andrey Kuznetsov (1)6-7 7-5 6-2.