Taylor Fritz is starting to make reaching big finals a habit. And he feels like he belongs among the very best players in tennis, too.

The American followed up his runner-up finish at the U.S. Open by beating Alexander Zverev 6-3, 3-6, 7-6 (3) on Saturday to advance to the final at the ATP Finals.

"I have believed that I belong, that I'm one of the best players," Fritz said. "It's not results-based. It's more I can feel how I'm playing. This week is huge."

In Sunday's final, Fritz will will face top-ranked Jannik Sinner — the player he lost to in the U.S. Open final. Sinner also beat Fritz in straight sets in the group stage this week.

Sinner advanced with a rapid 6-1, 6-2 win over Casper Ruud.

Fritz became the first American finalist since James Blake lost the 2006 final to Roger Federer. The last American to win the elite eight-man event was Pete Sampras, who beat Andre Agassi in 1999.

"I trust my game and I trust my level and I don't feel nearly as uncomfortable in these situations anymore because I've been playing the top guys at big events a lot lately," Fritz said. "I'm getting more comfortable in the moment. I'm really, really confident in my game."

If Fritz wins the trophy, it will mark an American sweep of the season-ending events after Coco Gauff won the WTA Finals last week.

Fritz's run in New York made him the first American man to reach a Grand Slam singles final in 15 years. He's playing at the ATP Finals for the second time. On debut two years ago, he beat Rafael Nadal in his opener and made it to the semifinals, losing to Novak Djokovic.

"It's awesome to come back and already go a step further," Fritz said. "I'm all about always trying to do better than the year before."

At the start of the week, Fritz told The Associated Press his "career has always been a very steady progression and just improving a little bit each year."

Fritz has Zverev's number

It was Fritz's fourth consecutive victory over Zverev, who replaced Carlos Alcaraz at No. 2 in the rankings this week.

"He's an uncomfortable player for me." Zverev said. "It's no secret."

Fritz, who is No. 5, also beat Zverev at Wimbledon and the U.S. Open, plus the Laver Cup.

Fritz is already assured of finishing the year in the top five for the first time and he'll rise to No. 4 on Monday if Ruud doesn't win the title.

Zverev has seen Fritz's improvement up close — especially on one key stroke: "His forehand used to break down quite a lot. His forehand was always fast, very aggressive, but it was very, very shaky in important moments. He could hit a winner, but he could hit the fence as well. I feel like the ratio is a lot more towards winners now."

It was a matchup of big servers between the 6-foot-5 (1.96-meter) Fritz and the 6-foot-6 (1.98-meter) Zverev, and when Fritz broke Zverev for 4-2 in the first set, it marked the first time that Zverev lost a service game in four matches in Turin.

Eventually, though, the match turned into a physical duel from the baseline. Fritz rallied from 0-40 and held his serve for 3-2 in the third after a nine-minute game full of long rallies — winning one such exchange that lasted 30 strokes.

Fritz was then under pressure one service game after another but somehow managed to keep holding.

Fritz got ahead early in the tiebreaker and finished Zverev off with an audacious inside-out forehand winner on his first match point.

"I lose at least one of those (break) points and that's probably it," Fritz said. "That's how it kind of goes with playing Sascha. Whoever takes their chances between the two of us is going to win the match just because you don't get too many and we're both big servers."

Fritz finished with 15 aces to Zverev's 10 in a match that last 2 hours, 20 minutes.

Zverev, the finals champion in 2018 and 2021, entered the semifinals on an eight-match winning streak after taking the Paris Masters.

"I felt like statistically and shot-wise, my level maybe was even higher than his until the important moments. That's where I kind of blew it," Zverev said. "This one will hurt more than the other few."

Doping case hangs over Sinner

Sinner is playing at home for the first time since it was announced before his U.S. Open title that he tested positive in two separate drug tests this year.

A decision to clear Sinner of wrongdoing was appealed by the World Anti-Doping Agency in September and a final ruling in the case is expected next year.

Last year, Sinner lost the final to Djokovic, who withdrew injured this year.