Tokyo,  America's Taylor Fritz battled back from 1-3 down in the deciding set to secure a 6-3, 6-7(5), 6-3 victory over Denis Shapovalov in the semi-finals to reach his third ATP Tour final of the season at the Japan Open Tennis Championships, here on Saturday.

Fritz thought he would have to miss the Japan Open after testing positive for Covid-19 in Seoul, where he had to quarantine for one week. But after arriving just in time for his Tokyo opener on Wednesday, the American has made the most of his opportunity by reaching the final at the ATP 500.

"It's pretty amazing what I've been able to accomplish this week," said Fritz, who benefitted from the withdrawal of Nick Kyrgios before their quarterfinal matchup.

"Just from thinking that I might not even be able to play this tournament to then seven days in a room, wake up at 5 a.m., take a flight here and just show up and play... It's pretty crazy how quickly things happen. It was only four days ago," he added.

Adding to the achievement, Fritz also clinched what will be his Top 10 debut in next week's edition of the ATP Rankings.

In an exhibition of first-strike tennis from both men in the Ariake Colosseum, the American was in control early behind his big serve and forehand. After saving a break point in his opening service game, he claimed the first set then broke for 3-2 in the second before Shapovalov fashioned an immediate reply.

The Canadian was fearless in winning a dramatic tie-break to force a third set.

After seeing a Fritz passing shot clip the line to erase a mini-break and knot the score at 4/4, Shapovalov ventured forward again on each of the next two points and was rewarded for his bravery. He then claimed the set by moving Fritz from corner to corner in a tense rally that was one of the longest of the match.

Gesturing to the crowd after sealing the set, Shapovalov then rode his momentum to a 3-1 lead in the decider. But a love hold helped Fritz rediscover his best form, as he rattled off the final five games of the match to set up an all-American final against his Laver Cup teammate Frances Tiafoe.

The standout stat of the semi-final was Fritz's 82 percent win rate (47/57) on the first serve.

All three of his victories this week have come in three sets, with Fritz also winning the first and third sets against James Duckworth and Japan's Hiroki Moriya.

After initially saying he was concerned with his fitness after falling ill and spending a week in lockdown, Fritz was presented with a new challenge in adapting to the "extremely fast" conditions on the stadium court.

"Honestly, physically I've felt fine all week. I think the biggest struggle for me this week has been the court speed," he said after reaching the final.

Due to persistent rain in Tokyo, Fritz was only able to practise on the venue's indoor courts. But he was able to hit on the show court on Friday evening after receiving a walkover from Kyrgios, and again early Saturday afternoon.

"I felt like that made a really big difference with my confidence and my feet hitting the ball," he said.

Fritz's victory set up the first all-American final in Tokyo since Pete Sampras defeated Richey Renenerg in 1996, in what was the fourth straight all-U.S. final at the event. By winning his third Tokyo title, Sampras completed a five-year run of American champions that also included two triumphs for Jim Courier.

Fritz holds a 4-1 ATP head-to-head series lead against Tiafoe, who advanced to the final with a 6-2, 0-6, 6-4 victory against Soonwoo Kwon earlier in the day.

Tiafoe's run in the Japanese capital has so far lifted him two spots to No.17 in the ATP Live Rankings, and the American could rise as high as No.15 should he lift his second ATP Tour title (Delray Beach 2019). Either mark would be a new career high for the 24-year-old.

On the other hand. Kwon was seeking his second tour-level final after his 2021 title run in Astana. In his Tokyo main-draw debut, the World No. 120 became the lowest-ranked semi-finalist at the ATP 500 since World No.140 Bohdan Ulihrach in 2004.