Dan Evans claimed his Indian Wells collapse was “more upstairs than downstairs” after he missed his chance to crack the world’s top 20 for the first time.
The British No 1 led by a set and a break against No 11 seed Diego Schwartzman after winning seven consecutive games in the midday sun.
And the world No 22 had two break points to lead 4-1 in the second set – and again at 4-4 to serve for the match at the BNP Paribas Open in California.
But Evans, who has recently suffered from Covid, could not keep running against one of the few men shorter than him on the ATP Tour – 5’7” Schwartzman.
And the robotic Argentine claimed the rollercoaster encounter by taking the last eight games to win 5-7 6-4 6-0 in two hours and 19 minutes.
Evans, who missed the Olympics after testing positive for Covid, said: “My legs were fine.
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“Three full sets isn’t an issue for me. Nor is five sets. I obviously played a pretty poor game at 4-3 and lost my focus.
“Then he got pretty hot and it just ran away from me really. It was more upstairs than downstairs. I feel like my game is in a good place.
“Today is a hiccup. It was not a great end to the trip. With a bit more focus, I could have been out of there in two sets.
“And we would be having a different conversation here and nothing about my legs. It was a bad end to the match.
And the Belarussian followed up the win by beating former Wimbledon champion Halep 7-5 6-4.
Sasnovich will now face another former world No 1 and double Grand Slam champion Victoria Azarenka in the fourth round on Tuesday.
“We never play against each other,” Sasnovich said. “But it is an unbelievable draw with four Grand Slam champions in my section.
“Raducanu, Halep and now Azarenka after she came through against Petra Kvitova. Vika is like Simona – one of the strongest character on tour. She’s a big fighter.
“I love the style she plays tennis. She has a nice plan with each player she plays.I will prepare and have my own plan how to play Vika. Yeah, it will be very interesting.
“It’s nice. For the long time we are on tour and I never play against her so it’s interesting. Two Belorussian player in the fourth round, it’s nice.”