No. 2 Novak Djokovic and No. 4 David Ferrer won their quarterfinals matches Thursday at the U.S. Open in Flushing Meadows, N.Y., and face each other in the semifinals.

Djokovic won in straight sets, 6-2, 7-6 (7-3), 6-4 over Argentina's Juan Martin del Potro to end Day 11 of the tournament. Before Djokovic's victory, Ferrer outlasted No. 8 Janko Tipsarevic in five sets, 6-3, 6-7, 6-2, 3-6, 7-6 in a match that lasted some 4 hours and 41 minutes. The last set alone took 84 minutes.

Ferrer had six double-faults to his opponent's zero, but also won the battle of services aces 15-10.

Djokovic hit 43 winners to del Potro's 25 in their match. The winner of Djokovic-Ferrer faces the winner of the Andy Murray-Tomas Berdych match in the U.S. Open final this weekend.

The women's singles semifinals take place Friday. It's top-seeded Viktoria Azarenka vs. No. 3 Maria Sharapova, and No. 4 Serena Williams against the surprise semifinalist, No. 10 Sara Errani of Italy.

The No. 2 Bryan brothers, Bob and Mike, play for the men's doubles title against No. 5 Leander Paes and Radek Stepanek.

For more updates on the 2012 U.S. Open, check out SB Nation's tennis hub. Live scores can be viewed at the event's website.