Roberto Bautista Agut has taken down a Grand Slam champion…

In an exciting five-set match, the 26-year-old Spanish professional tennis player outlasted No. 5 seed and former U.S. Open champion Juan Martin del Potro in the second round at the Australian Open, pulling off the biggest upset of the Grand Slam event so far.

The Argentinian del Potro led twice in sets, before Bautista Agut –ranked No. 62 in the world – fought back to seal a 4-6, 6-3, 5-7, 6-4, 7-5 victory under the lights in Melbourne.

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 three hours and 53 minutes, and ended at 1:20 am Melbourne time on Friday after a long day of suspensions and delays in matches due to extreme heat and storms.

It’s a tough loss for del Potro, who 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.

Bautista Agut next faces No. 27-ranked Benoit Paire in the third round.