Fifth-seeded Juan Martin del Potro has been eliminated from the Australian Open in the biggest upset of the tournament this week, beaten 4-6, 6-3, 5-7, 6-4, 7-5 by Roberto Bautista Agut of Spain.

It was Bautista Agut’s first win in seven matches against a top 10 player, and del Potro’s fourth second-round exit in eight years at the season’s first major.

The match lasted 3 hours and 53 minutes and ended at 1-20 a.m. Friday after a long day of match suspensions and delays due to extreme heat and storms.

“I think he played a great match over nearly four hours,” del Potro said. “But in every (important) moment ... he played an unbelievable shot. In breakpoint down, he served well. He made winners with forehands, backhands, and he played always down the line very often.”

Bautista Agut had only ever played two five-set matches, losing both, and is now into the third round of a Grand Slam tournament for the first time.

Del Potro won his 18th career singles title last week by beating Bernard Tomic in the final of the Sydney International, a key warm-up event for the Australian Open, and was considered the leading contender from outside the “Big Four” for the Australian title.

“The season has just started,” del Potro, the 2009 U.S. Open champion, said. “I will try to be positive for the rest of the year.”

Sloane Stephens survived a close call against 67-ranked Ajla Tomljanovic Thursday, rallying to beat the Croatian 3-6, 6-2, 7-5 at the Australian Open after a lengthy lightning delay.

The 13-seeded Stephens, who beat Serena Williams on the way to the semifinals last year, came back after dropping the first set to capture seven straight games and take a 3-0 lead in the third set before play was suspended.

When the players returned to the court, Tomljanonvic reeled off five straight games and was serving for the match at 5-4 when she double-faulted to allow Stephens to break back and eventually close out the match.

Stephens arrived in Melbourne with a new coach, Paul Annacone, who had previously worked with Roger Federer.

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