WIMBLEDON, England - Roger Federer has already been through a “serving contest” at Wimbledon this year. It’s probably nothing compared to what’s coming next.

Federer used the term after his fourth-round match, which included two tiebreakers and only one break of serve. Up next in Wednesday’s quarterfinals is Ivo Karlovic, who makes a living smacking aces and service winner.

The 6-foot-10 Croat — the tallest player in the history of the ATP tour — has not been broken once in 79 service games this tournament and leads all players with 137 aces. He hit 46 of those in his third-round upset of No. 9 Jo-Wilfried Tsonga, a four-set win that included three tiebreakers.

Federer, however, has an 8-1 record against Karlovic — with 12 of the 22 sets ending in tiebreakers — despite few chances to show off his all-court game.

“I like those sorts of challenges,” said Federer, who is seeking his sixth Wimbledon championship and record 15th Grand Slam title. “It’s maybe not the most fun match to go through. But I like to beat this guy, because he makes it hard on us to beat him.”

The quarterfinal round features players of eight nationalities, with five Grand Slam tournament winners and four former No. 1s.

Federer plays the first match on Centre Court on Wednesday, which despite his immense popularity at the All England Club is seen by many Brits as merely the opening act for the second encounter, when Andy Murray takes on Juan Carlos Ferrero of Spain.

On Court 1, two veterans are trying to get back to the Wimbledon semifinals for the first time in four years. Andy Roddick, the runner-up to Federer in 2004-05, takes on Lleyton Hewitt, who won here in 2002.

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The fourth matchup features the oldest remaining player against the youngest, with the 31-year-old Tommy Haas taking on 22-year-old Novak Djokovic.

Federer is coming off a win over Robin Soderling that he called “pretty much a serving contest.” It was a rematch of the French Open final, when Federer completed a career Grand Slam.

Karlovic is often dismissed as a one-trick pony — he breaks serve about as seldom as he loses it — and has reached the quarterfinals for the first time in 25 career Grand Slam tournaments. Despite having two grass-court titles to his name, Karlovic was eliminated in the first round at Wimbledon the last four years.

But Federer said Karlovic has developed more aspects of his game.

“He’s become an excellent player,” Federer said. “Not only just his serve, he’s got to have something more, otherwise he wouldn’t be ranked where he is and he wouldn’t be beating all those good players. He’s not to be underestimated.”

The problem for the top players is that a tiebreaker against Karlovic is often a coin-flip, where losing a single point on serve can be decisive. In 296 career matches, Karlovic has played 318 tiebreakers — winning 51 percent of them.

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Of course, Federer wouldn’t be Federer if he wasn’t at his best in pressure situations, and the Swiss star has won nine of the 12 tiebreakers against Karlovic.

“The reason why he was No. 1, and also why he’s maybe the best player ever, is because in the tight situations he can play his best tennis,” Karlovic said. “It is difficult, sure.”

Murray is coming off perhaps the most memorable match of the tournament so far, a five-set win over Stanislas Wawrinka played Monday underneath Wimbledon’s new retractable roof for the latest finish ever on Centre Court.

The 22-year-old Scot has never reached the semifinals at Wimbledon but faces ever-increasing pressure from the home fans to deliver the first British men’s title since Fred Perry in 1936. His win against Wawrinka — the first match played entirely under the roof — was seen by more than 12 million viewers on BBC, more than twice its average audience for that time slot.

Murray beat Ferrero, the only remaining wild card, in straight sets at Queen’s Club this month, but is expecting a tougher challenge this time.

“Ferrero is a very tough player. He plays well on any surface,” Murray said. “If I play poorly, there’s a good chance I’ll lose against him.”

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