Olympic gold medallist Alexander Zverev and French Open runner-up Stefanos Tsitsipas slumped to shock quarter-final exits in the ATP Indian Wells Masters, losing in three sets at the main stadium on Friday.
American Taylor Fritz survived two match points to come from behind and eliminate third seeded Zverev 4-6, 6-3, 7-6 (7/3) while second seeded Tsitsipas was shown the door 6-4, 2-6, 6-4 shortly after by world number 36 Nikoloz Basilashvili.
The exits of Zverev and Tsitsipas means Great Britain's Cameron Norrie, who is seeded 21st, is the top seed left in the final four.
The semi-finals are now set with 31st seeded Fritz facing Basilashvili and Norrie going up against 23rd seeded Grigor Dimitrov for a spot in Sunday's championship match at the Tennis Garden in the California desert.
Germany's Zverev jumped out to a big lead in the final set and appeared to be heading to victory before he started to struggle mightily on his second serve.
"This one hurts because I knew that after Stefanos lost this morning, I was kind of the favourite to win this tournament," said Zverev. "But my tennis wasn't there."
He blasted a 135 mph ace to get to match point but then immediately double faulted and Fritz won the next point to take the game and cut the lead to 5-4.
Crowd favourite Fritz dominated the third-set tiebreaker clinching the match with a cross court forehand winner.
"I put myself in a situation to get back into it and I did," said Fritz, of San Diego. "I just kept fighting and went after my shots and kept playing my game."
This was just the second loss for Zverev since losing in the fourth round at Wimbledon. Zverev is 20-2 over that stretch.
Tsitsipas also fell in three sets to the 29th seeded Basilashvili, who recorded one of his biggest career wins.
Georgia's Basilashvili beat Tsitsipas for the first time in three career meetings and recorded his first win over a world number three player.
He defeated Roger Federer en route to the Doha title in March, when the Swiss great was playing just his second match since a 13-month injury absence.
Leading up to Indian Wells, Basilashvili said he had been working on polishing his serve.
"I am not surprised. I have been playing good tennis for a long time especially in practices," he said. "I just didn't have the kind of first serve. It was missing. I had big minus in my serve.
"I improved my serve a lot lately. That's why I'm in the semis now."
Basilashvili had never won a round in Indian Wells until this year's tournament.
Tsitsipas, of Greece, blasted 10 aces but made two double faults and was undone by unforced errors in the two hour, 10 minute match on the main stadium.
Basilashvili jumped out to early leads by breaking Tsitsipas in the opening games of the first and third sets. He won four of the final five games in the third and clinched the match when Tsitsipas blasted a backhand wide.
"I was under stress. My energy level was going up and down but I am happy with the way it ended and I kept my energy level up," said Basilashvili, the son of a Georgian national ballet dancer. "At the end I was really tired but I was physically able to stay on the court."
Besides saving a match point to beat Federer on the way to the title in Doha, Basilashvili also won his fifth career title in Munich in May.
After Friday's win, Basilashvili said beating his hero Federer had been a springboard.
"My win against Roger meant a lot to me because he was my idol," Basilashvili said. "Roger's win was very important in my career. Beating Stefanos today was as well, a really, really important match."