Mardy Fish moved into the semifinals of the Countrywide Classic in Los Angeles on Friday with a 6-4, 6-4 win over Florent Serra of France. Also advancing were No. 3 seed Juan Martin del Potro of Argentina, a 7-6 (6), 6-2 winner over American Amer Delic, and German left-hander Denis Gremelmayr, who upset No. 5 seed Marat Safin, 3-6, 6-3, 6-2.