Video: John Isner beats Novak Djokovic in Cincinnati

Rafael Nadal defeats Roger Federer to advance to the semifinals of the Western & Southern Open on Friday – and Wimbledon champion Andy Murray is knocked out of the tournament 6-3, 6-4 by Tomas Berdych

It was quarter finals day at the Western & Southern Open in Cincinnati on Friday and up first World number one Novak Djokovic faced John Isner.

With the game evenly poised at one set all the match went into a decider.

Despite Djokovic building momentum from the second set, Isner refused to wilt.

The American made his march in the 12th game, and while Djokovic saved the first match point with an ace, he double faulted at the crucial time and Isner sealed a memorable win.

Isner will play seventh-seeded Juan Martin del Potro of Argentina in the last four.

The Argentinian overcame Russian qualifier Dmitry Tursunov 6-4, 3-6, 6-1.

Wimbledon champion Andy Murray faced Tomas Berdych but was knocked out in straight sets 6-3, 6-4.

Murray was playing in his last match before he attempts to defend his US Open title later this month.

Berdych will face Rafael Nadal in the semi-finals after he overcame Roger Federer.

Nadal has now won 21 matches against Federer, compared to the 10 head to head wins of his Swiss rival.

Nadal secured a 5-7, 6-4, 6-3 victory.