Top-seeded Gael Monfils of France beat No 11 John Isner 6-4, 3-6, 7-6 (6) in a rain-delayed match on Saturday to advance to the final of the Legg Mason Tennis Classic.
Monfils will meet Radek Stepanek on Sunday after the Czech defeated American Donald Young 6-3, 6-3.
Monfils, ranked seventh in the world, won the tiebreaker when the lanky Isner hit a forehand into the net.
Isner staved off two match points in the 10th game. On the second, Monfils felt Isner's serve was wide, but the replay machine failed to operate, and the call stood.
The start of the match was delayed nearly two hours. There were two lengthy rain delays and the match finally ended at 1:15am local time.