Roger Federer served his way into the quarter-finals at Wimbledon with a straight-sets victory over Lleyton Hewitt. The world No 1 hit 21 aces as he beat the 2002 champion 7-6 (9-7), 6-2, 6-4 in the fourth round on Centre Court.

"I think I served really well which was important against Lleyton," Federer said. "I saw he was struggling with his hip but nevertheless, he was dangerous. I think the key was the first set tie-break and afterwards I played consistently well and saved a lot of break points which was crucial."

Neither player could force a break point, or even take a game to deuce, in a cagey opening set which required a tie-break to decide it. Hewitt, the last man to win Wimbledon before Federer's five consecutive titles, looked like going 3-0 down before a correct challenge via Hawk-Eye, but the Australian still found himself having to save three set points.

It was then Federer's turn to win a crucial challenge at 7-7 and the champion took full advantage. A brilliant backhand winner down the line, after he had drawn Hewitt into the net, gave the Swiss another set point and he took it with an ace to win the tie-break 9-7.

Hewitt's hopes of causing a massive upset had surely rested on him winning the opening set, and it was no surprise when he dropped his serve in the first game of the second. A host of unforced errors, including a double fault, gifted Federer the advantage and it was the same story in the third game as the No 1 seed stormed into a 4-0 lead.

Hewitt finally got on the scoreboard with a love service game and even forced a break point in the next game, but Federer responded with his 13th and 14th aces of the match to avert the danger. The defending champion saved two more break points to close out the set 6-2 and all but guarantee his place in the quarter-finals.

Hewitt has been struggling with a hip injury and appeared occasionally to grimace in pain, but he didn't throw in the towel, forcing five break points on Federer's first two service games of the third set. However, the Swiss saved them all with some superb serving and, in between, broke Hewitt's serve once more.

The Australian kept Federer within his sights but the five-time winner looked to have plenty in reserve, serving out to complete victory in 1hr 49 mins.

Federer will play Mario Ancic in the quarter-finals on Monday after the unseeded Croatian came back from two sets down to beat Fernando Verdasco, of Spain, 3-6, 4-6, 6-3, 6-4, 13-11.