MELBOURNE, Australia (AP) -- top-ranked Rafael Nadal and Wimbledon champion Andy Murray faced tougher-than-expected matches to advance to the quarterfinals at Melbourne Park.
Nadal won three tough sets against Kei Nishikori, while Murray wasted four match points in the third set - including two in the tiebreaker - before dominating the fourth set against lucky loser Stephane Robert of France.
Sixth-seeded Roger Federer has equaled Jimmy Connors record by reaching his 41st Grand Slam quarterfinal with a 6-3, 7-5, 6-4 win over Jo-Wilfried Tsonga in the fourth round of the Australian Open on Monday.
It was also the 11th straight year the Swiss star has reached the quarters at Melbourne Park.
Federer next faces Murray in the quarterfinals. He has won just four of his last 14 matches against top-10 players, including Monday's victory over 10th-seeded Tsonga.
Nadal beat Nishikori 7-6 (3), 7-5, 7-6 (3), though he was broken twice in the third set - getting a time violation from chair umpire Evanthia Asderaki in one of the games.
''Normally I have a good self-control on court, and it's true that the moment was a very critical one,'' Nadal said of the time violation.
The 13-time major winner also tripped in the first set and tumbled to the court, then had to go to the locker room to change shoes.
Nadal next plays Grigor Dimitrov, who reached the quarterfinals of a Grand Slam for the first time with a 6-3, 3-6, 6-2, 6-4 win over Roberto Bautista Agut.
Dimitrov advanced to his first Grand Slam quarterfinal in his 14th attempt after beating Roberto Bautista Agut 6-3, 3-6, 6-2, 6-4 at the Australian Open on Monday.
Dimitrov, who beat No. 11 Milos Raonic in the third round, clinched the match by breaking Bautista Agut's serve for the fourth time.
Three-time Australian Open finalist Murray ended the run of Robert, wasting match points in the third set and smashing his racket after the tiebreaker before advancing 6-1, 6-2, 7-6 (6), 6-2.
''He's a fun player to watch, but not a fun player to play,'' Murray said of Robert's assortment of drop shots and deft groundstrokes.
The racket smashing was pure frustration.
''Losing that set was frustrating because it obviously means you're out there another 30, 40 minutes at least, when I would preferably had been in the locker room,'' Murray said. ''My racket bit the dust. Unfortunate for it.''
Murray said he's expecting a tough match against Federer, regardless of the Swiss player's recent drop in the rankings that has seen him seeded sixth here.
''I think last year you could see at periods he was struggling with his back,'' Murray said. ''And if he's fully fit, I've said all along, he's always going to be there or thereabouts in the majors, and he'll give himself opportunities to win more because he's that good.''
Federer lost to Murray in the semifinals last year in five sets after beating Tsonga in five in the quarterfinals.
''It's the same draw just one round earlier for me,'' Federer said. ''I'm happy this time I didn't play five sets.''
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