Team USA went through to the United Cup final in Sydney in bizarre circumstances after Tomas Mahac retired from his match with Taylor Fritz. The Czech player needed no less than a win after Coco Gauff had beat Karolina Muchova to give the Americans a 1-0 lead, and looked win course to level the tie after taking the first set 7-6(4).

And the 24-year-old was on the brink of victory when he had two match points at 5-2 in the second, although Fritz survived.

Still, he served for the match with 5-3 but again failed to take the opportunity, and frustration began to boil over as Fritz also won the next two games to serve for the set at 6-5.

But he never had to complete the job. Mahac hurled his racquet to the ground during the changeover and was seen arguing wildly with his coach before coming back out on to the court.

He immediately went 15-0 love down after a wild forehand return, and at that point the world No.25 decided enough was enough. After taking his hat off, he approached the umpire to explain he was retiring with cramps.

Mahac did shake his hands with his opponent, and the pair had a brief conversation at the net. But he still cut an angry figure as he left the court, with it unclear if he raging at his team or the fact he felt forced to retire.

It all meant Fritz was gifted the win and sent the USA through to the final against Team Poland. And despite appearing confused afterwards, the 27-year-old did reveal that Mahac had claimed afterwards to have been affected physically during the second set.

“He said he’d been cramping for a couple games already” said Fritz. “I didn’t notice, but yeah. He was moving pretty well, but I guess he was playing through it, fighting. It’s really humid in here.

“That’s something I was thinking was a possibility if I could win that set, take it to a third, I was thinking maybe someone might start cramping later on. It’s tough conditions, it was a physical match.”

Poland meanwhile, booked their place after also taking an unassailable 2-0 lead against Kazakhstan. Hubert Hurkacz put them on their way with a 6-3 6-2 victory over Alexander Shevchenko.

World No.2 Iga Swiatek then sealed the deal with a a 7-6 (7-5) 6-4 win over Elena Rybakina. The final of the tournament, which traditionally helps players build-up for the final of the Australian Open, takes place on Sunday.