ROGER FEDERER said he had “flushed away” the pain of his defeat in the Wimbledon final as he prepares for a rematch against Novak Djokovic after keeping alive his hopes of a seventh ATP Finals crown Tuesday.

The Swiss put himself back into the mix at the end-of-season event with a 7-6 (7/2), 6-3 win against Italian debutant Matteo Berrettini.

The third seed had put himself under enormous pressure by losing his first round-robin match in Group Bjorn Borg on Sunday to Dominic Thiem.

The six-time champion was not at his fluent best Tuesday but ultimately had too much for his Italian opponent, who had won just three games against Djokovic in his opener.

Federer, 38, will face the Serbian second seed today in a repeat of July’s marathon Wimbledon final, during which he squandered two championship points on his own serve.

The Swiss was asked after his win against Berrettini whether that defeat had left emotional or mental scars.

“We’ll find out, but I think it’s all flushed away from my side,” said Federer, who added that it had taken him two weeks at most to get over the loss.

“A lot of water has gone under the bridge since then.

“We have played a lot of matches since, and I think we both look back at a great match. I think we both can take away some confidence from the match.”

He added: “Actually, it’s good for me to play him again, and maybe that all helps to get a chance to get him back or whatever it is, but at the end of the day, I’m here for the World Tour Finals and not because of the Wimbledon finals.”

Meanwhile, Dominic Thiem landed one too many punches even for Novak Djokovic to handle.

In a seesawing crowd pleaser that lasted nearly three hours and featured a handful of momentum shifts in the third set, Thiem outlasted Djokovic 6-7 (5), 6-3, 7-6 (5) Tuesday to become the first player to advance from the group stage at the ATP Finals.

“It was maybe the best match I ever played,” said Thiem, a two-time French Open runner-up. “It was a real classic and epic match, which will happen from time to time at these big tournaments. It had everything — He was up; I was up. He was playing amazing points. Me, I was playing amazing points.”

Djokovic twice rallied from a break down in the third set and led 4-1 in the tiebreaker, but Thiem then won five straight points — taking his total number of winners to 50 for the match — before converting his second match point.

“I don’t think I have experienced too many matches like this where my opponent just goes for every single shot,” Djokovic said. “I mean, he was unbelievable.”

The result leaves Djokovic facing a winner-takes-all match against Federer — in a highly anticipated rematch of this year’s Wimbledon final — to decide who will join Thiem in the semifinals.

Thiem, for his part, has now beaten Djokovic in four of their last five meetings — although the previous three wins came on clay, his favorite surface.

In the best match of the tournament so far, Djokovic needed to play near flawless tennis in the first set — making just two unforced errors — to hold off the Austrian.

At 65 minutes, the first set alone was longer than Djokovic’s entire straight-sets win over Berrettini on Sunday. (SD-Agencies)