Published: Oct 02, 2012 5:25 AM EDT
Updated: Oct 03, 2012 6:32 AM EDT

TOKYO (AP) - Andy Murray opened the defense of his Japan Open title by beating Ivo Karlovic of Croatia 7-6 (7), 6-4 in the first round on Tuesday.

Murray withstood 17 aces from Karlovic at Ariake Colosseum.

Gael Monfils of France, who was scheduled to be Murray's opponent, withdrew with a right knee injury he aggravated in Beijing last week, and was replaced by lucky loser Karlovic. Monfils is returning to Paris to have his knee examined.

Despite having break points in the first and seventh games, Murray was unable to capitalize.

Murray, who bested Karlovic in the first round at Wimbledon, serve three consecutive aces in the eighth game to level at 4-4.

With both players unable to break serve, Murray finally prevailed 9-7 in the tiebreak with a forehand passing shot down the line, after saving a set point when he was down 7-6.

Karlovic, who had 12 aces in the set, squandered a chance to go up 6-3 in the tiebreak when he double-faulted.

Murray, the U.S. Open and Olympic champion, took an injury timeout following the first set after appearing to injure his back early in the match.

The second set was on serve until the 10th game, when Murray went up 0-40 with Karlovic serving. The Croat saved two match points, but sent a forehand long on the third to give Murray the victory.

In other matches, sixth-seeded Milos Raonic of Canada defeated Radek Stepanek of the Czech Republic 6-4, 6-4, while eighth-seeded Kei Nishikori of Japan ousted compatriot Go Soeda 4-6, 6-2, 6-3.

Tommy Robredo of Spain topped Jarkko Nieminen of Finland 6-2, 6-4; Jeremy Chardy of France downed wild card Yuichi Sugita of Japan 6-1, 7-5; and qualifier Dmitry Tursunov of Russia dispatched Bernard Tomic of Australia 6-4, 7-5.