LONDON - Top-seeded Andy Murray stayed on course for a record-tying fourth title at Queen's Club by defeating Fernando Verdasco 7-5, 6-4 in the second round on Thursday.

Murray is attempting to join John McEnroe, Boris Becker, Andy Roddick and Lleyton Hewitt as a four-time winner, and broke Verdasco for the second time to claim the first set.

Verdasco wasted four break points in Murray's first two service games in the second set, but the Spaniard was broken again in the final game when he hit a backhand wide on Murray's second match point.

"I thought it was fine," Murray said of his performance. "I felt like I dug myself out of a few difficult situations when I was behind on my serve. Especially in the second set, I played some good points there, a few aces, like right in the right spots, a few onto the line at big moments."

Defending champion Grigor Dimitrov lost to Gilles Muller of Luxembourg 6-4, 7-6 (5). The sixth-seeded Dimitrov won the title last year by defeating Feliciano Lopez, but has failed to reach a final since. He was bidding to successfully defend a title for the first time in his career.

In a match of few rallies in which Muller had 19 aces and Dimitrov 15, the Bulgarian double-faulted at 5-4 in the first set, and made a forehand error to give Muller the only break of the match and the first set.

Dimitrov saved a break point at 2-1 in the second with a backhand winner down the line, but Muller was stronger in the tiebreaker.

"I don't think I'm playing bad tennis at the moment," Dimitrov said. "I just am doing a lot of good things on the court which really don't discourage me to play. Of course, it's a tough loss for me, but I give credit to Gilles. He played a good match."

In another big-serve show in which John Isner hit 36 aces and Feliciano Lopez 29, Isner made the quarterfinals with a 7-6 (5), 6-7 (9), 7-6 (4) victory.

Lopez earned the first break point of the match at 5-4 in the second set, and although Isner saved the set when Lopez returned wide, the Spaniard went on to save two match points and claim the second tiebreaker on his fourth set point.

Isner earned two more match points at 5-4 in the final set, before securing victory in the tiebreaker on his sixth match point.

Fourth-seeded Marin Cilic failed in his bid to repeat his 2012 title run when the Croatian was defeated by Serbia's Viktor Troicki 6-7 (8), 6-2, 6-3. Troicki didn't drop his serve, and broke Cilic three times.