Mardy Fish held off big-serving John Isner 6-2, 6-7, 7-5 in the second round of the San Jose Open on Thursday.
Fish took the first set convincingly and led 3-0 in the second set tiebreak before his 6-foot-9 opponent battled back to even the match.
But the opportunistic Fish broke Isner while leading 6-5 in the final set to close out the match.
He had 13 aces to Isner's 15.
"He's uncomfortable to play," Fish told reporters.
"You just have to hang in there the best you can and hope to get an error or two. He's the kind of player on any given day who can beat anyone."
Isner almost proved it against the fifth-seeded Fish until the American took advantage of a subdued final service game from his opponent.
Isner made two errors to fall behind 15-30 and missed a short backhand volley to open the door.
In other second-round action, top-seeded Andy Roddick dispatched Latvian Ernests Gulbis 6-3, 7-6 (3) while James Blake enjoyed a straight sets win over Florent Serra, defeating the Frenchman 6-4, 6-3.
Argentine second seed Juan Martin Del Potro won 6-2, 6-2 against Kei Nishikori of Japan.
Sam Querrey knocked out Denis Gremelmayr of Germany 6-3, 6-2 and Todd Widom defeated Taylor Dent 6-7, 6-3, 6-2.