Queen's 2015: Champion Grigor Dimitrov suffers early exit

Grigor Dimitrov (left) won the 2014 competition by beating Spain's Feliciano Lopez in the final

Grigor Dimitrov's title defence at Queen's Club ended with a straight-sets defeat by Gilles Muller of Luxembourg in round two.

Muller, 32, hit 19 aces as he won 6-4 7-6 (7-5) to reach the quarter-finals of the Aegon Championships.

The world number 48 goes on to face Andy Murray or Fernando Verdasco.

"I've been coming here for a long time and it was my first time on Centre Court," Muller told BBC Sport. "It's tough to beat that."

Asked if it hurt more to lose as the defending champion, Dimitrov said: "It always does. It's a tough loss for me, but I give credit to Gilles. He played a good match. Very solid serving."

The 24-year-old, who lost in the first round of the French Open last month, next heads to Wimbledon where last year he beat Andy Murray on his way to the semi-finals.

"I've just got to go out there and perform," he added.

"I felt I have been quite unlucky in the past weeks with a lot that has been going on, and it's something that actually I accept and I need to fight through."

In Halle, Germany, second seed Kei Nishikori advanced to the quarter-finals of the Gerry Weber Open by beating German wildcard Dustin Brown 7-5, 6-1.

The Japanese player next faces Poland's Jerzy Janowicz, who earlier defeated Colombian qualifier Alejandro Falla 6-2, 5-7, 6-2.