Tallon Griekspoor upset top seed Alexander Zverev 4-6 7-6(5) 7-6(4) in a marathon second round clash at Indian Wells on Friday.
The Dutchman collapsed on the court after converting his sixth match point to end an absorbing three hour, seven minute affair under sunny skies on Stadium One court.
"I'm incredibly proud. It was such a mental battle to beat him," Griekspoor said after claiming the win over the German, who had dominated their head-to-head matchups coming into the contest.
"I beat him once but then lost the next six times so it was such a mental thing. Happy to finally get it out of the way."
Zverev served for the match in the second set but was unable to get over the line and Griekspoor edged him in the second set tiebreaker to force a decider.
Griekspoor failed to convert five match points with the match on his racket at 6-5 in the third but regrouped to take the deciding tiebreak.
It was Griekspoor's first win over a top five opponent in 19 attempts.
"Finally," Griekspoor wrote with a smiley face on the TV camera lens after the hard-fought victory.
Griekspoor will face big-serving Frenchman Giovanni Mpetshi Perricard in the third round.
Zverev has struggled with his form and is 4-4 since losing to world number one Jannik Sinner in the Australian Open final in January.
"I'm just not playing good tennis at the moment. It's as simple as that," he told reporters.
"I'm not playing a level that I want to play, definitely not playing anywhere near what I played in Australia.
"I'm just disappointed with my game."
The world number two said he would need to go back to the drawing board.
RUUD UPSET
Fourth seed Casper Ruud fell to American Marcos Giron 7-6(4) 3-6 6-2 in the other big upset of the day.
Giron was ecstatic after shocking the Norwegian, leaping into the air and shouting as the crowd erupted after he reached the third round of the tournament for a second time.
"That was an amazing win. It will be one I look back on with amazing memories," Giron said.
"To do it here at my favorite tournament is special. It was the tournament I came to when I was younger and it was an amazing atmosphere.
Popular 10th seed Tommy Paul eased past fellow American Tristan Boyer 6-3 6-1 in front of a packed stands on court three and will face Britain's Cameron Norrie, who defeated 23rd seed Jiri Lehecka 3-6 6-4 7-5.
Eighth seed Stefanos Tsitsipas failed to convert his first match point while his opponent was down on the court but ultimately prevailed 6-2 6-4 over Thiago Seyboth Wild.
Dane Holger Rune, seeded 12th, will face 18th seeded Frenchman Ugo Humbert in the third round after they both enjoyed straight-sets victories on Friday.
Russia's Daniil Medvedev, the finalist in Indian Wells the last two years, made quick work of China's Yunchaokete Bu with a straight sets win.
"6-2 6-2, 1:36 minutes, very fast court," Medvedev wrote on the TV camera lens in reference to his ongoing complaints that the hard courts at Indian Wells are too slow even after they were resurfaced for this year's competition.
On the women's side, Iga Swiatek got her title defense off to a hot start in the desert, dominating Frenchwoman Caroline Garcia 6-2 6-0.
The Polish second seed will next face Ukrainian Dayana Yastremska, who upset Tunisian Ons Jabeur in straight sets earlier in the day.
Elena Rybakina was sharp in her first match at Indian Wells since winning the title in 2023, taking out Suzan Lamens of the Netherlands 6-3 6-3.
The big-serving Rybakina, who was born in Russia but represents Kazakhstan, missed the tournament last year due to illness.
Rybakina, seeded seventh, will face Britain's Katie Boulter in the third round after the 25th seed beat Irina-Camelia Begu of Romania 6-7(2) 6-3 6-0.
Fourth seeded American Jessica Pegula and 17-year-old Russian Mirra Andreeva both advanced in straight sets wins under the lights.
Earlier in the day Ukraine's 18th seed Marta Kostyuk and a pair of Czechs - 15th seed Karolina Muchova and Katerina Siniakova - also advanced to the third round of the WTA 1000 event.
