NEWPORT - Reilly Opelka hammered 27 aces in a 4-6, 6-3, 6-4 victory over Mackenzie McDonald on Thursday to book a semi-final meeting with Alex Michelsen at the ATP grass-court tournament in Newport, Rhode Island.
Opelka, playing on a wild card in his first tournament in almost two years, became the lowest-ranked player to reach a semi-final in the ATP era, having fallen to 1,188th in the world as he recovered from hip and wrist operations.
"There is a bit of a good element to that," said Opelka, who shocked top seed and defending champion Adrian Mannarino in the previous round.
"Let's just call it like it is, these guys don't want to lose to a guy that hasn't played in two years," Opelka said.
"I'm playing with house money. It allows me to be a little bit more free and there's extra nerves on the other side of the net."
But Opelka, who last played at Washington in 2022 when he was ranked 17th in the world, acknowledged he has some rust to shake off before a hoped-for appearance at the US Open in August.
"I was serving for it up 40-love and threw in two double faults. So that was a little bit out of character," he said. "But that's why I'm here. I'm here to try to shake off some of that rust -- better I think to do it here and get it out of the way as opposed to maybe (at the) US Open."
Third-seeded Michelsen, 19, is into the semi-finals for the second straight year thanks to a 6-4, 6-4 victory over fellow American Aleksandar Kovacevic.
Runner-up last year to Mannarino, he withstood 12 aces from Kovacevic and saved the only break point he faced.
In a match carried over from Wednesday, second-seeded Marcos Giron rallied from 0-3 down in the third set to beat France's Benoit Paire 4-6, 7-5, 6-4 and reach the quarter-finals.
Paire had led 6-4, 1-0 when darkness halted play on Wednesday evening.
After pocketing the second set, the 46th-ranked Giron was quickly in trouble in the third. But he took full advantage of Paire's miscues, including nine double faults, and booked a quarter-final meeting with Australian qualifier Alex Bolt.