Serving monsters John Isner and Kevin Anderson stand between Rafael Nadal and Novak Djokovic extending the big four's 15-year mortgage on tennis's most prized asset.
Nadal and Djokovic will clash in a box office Wimbledon semi-final on Friday night, with the winner of the 52nd instalment of their epic rivalry to face either Isner or Anderson in Sunday's championship decider.
Between them, three-times champion Djokovic, Nadal, fellow dual winner Andy Murray and dethroned eight-times king Roger Federer have won every men's singles crown since 2003.
Now the superstar quartet 's reign is under siege from serving bombers Isner and Anderson, who have rocketed down some 284 untouchable deliveries in their first-time forays to the final four at The All England Club.
In addition to his own 161 aces, the 208cm-tall Isner has won every single one of his 95 service games, facing a measly seven break points in five matches.
Little wonder the 33-year-old is feeling "pure elation" and ready to continue his title assault against the 10th-seeded Anderson.
"Very, very happy to be in this position right now in the semi-finals. With how I'm feeling physically and mentally, I'm in a very good spot. I think I can keep doing damage here," Isner said.
"This is amazing. It's by far the best grand slam I've ever played in my career, and I've been playing for 11 years. I'm super happy.
"To do it here at Wimbledon makes it even a little bit more special."
After taking out Federer in spectacular fashion from two sets down in their quarter-final, Anderson is a win away from a potential repeat of his 2017 US Open decider against Nadal.
The South African lost that match in New York in straight sets and is desperate for a shot at redemption, having learnt some harsh lessons from his maiden grand slam final appearance.
"I didn't give myself as much of a chance to win that match from a mental side," Anderson said.
"I feel like I'm doing a good job of keeping it in perspective. There's hopefully two more matches still to be played. I'm sort of more focused on that than getting too excited about the overall picture."
Isner, who famously unleashed 113 aces on Nicolas Mahut in his 11-hour, five-minute Wimbledon victory over the Frenchman in 2010, leads Anderson 8-3 head to head.
The American has won their past five meetings.
"We haven't played in a few years, which I think is a little bit weird," Isner said of his former American college rival.
"It's always close, always very close. When you match up with two big servers, inevitably the matches are going to be close.
"I'm going to expect a very tough match on Friday. I think he will expect that, as well."