The two took out a pair of former event champions in the semifinals on Saturday. Tsitsipas beat six-time champion Roger Federer in the afternoon session, 6-3, 6-4, and Thiem outslugged defending champion Alexander Zverev, 7-5, 6-3, to close out the night.
Tsitsipas, who saved 11 of 12 break points against Federer, has held 44 of his 47 service games this week. He was broken once by Federer and twice by Rafael Nadal in his last round-robin match.
“I remember myself being one of these kids here, watching the event,” he said after his semifinal win over Federer. “I could never picture myself standing here, but it did happen. Dreams do come true.”
Tsitsipas has three career ATP titles, all of which have come at the 250-level. His biggest previous final came at ATP Masters 1000 events in Toronto last year and Madrid this year, where he fell to Nadal and Novak Djokovic, respectively.
“This does feel, in a way, like a Grand Slam, because all eyes are here,” Tsitsipas said. “Everyone who watches tennis knows what the Nitto ATP Finals are. For me it’s a great new start, great new beginning to be here, playing in the Finals. I would compare it almost as a Grand Slam for sure, but you have less matches. It’s very difficult to get to the position I am in right now, and it counts a lot.”
Already the first Greek ever to qualify for the ATP Finals, Tsitsipas could become just the third player in the last 40 years to win the season-ending title in his tournament debut, after Alex Corretja in 1998 and Grigor Dimitrov in 2017. Four players did it in the ‘70s: Stan Smith in the first year of the tournament in 1970, then Ilie Nastase in 1971, Guillermo Vilas in 1974 and John McEnroe in 1978.
Unlike Tsitsipas, Thiem isn’t playing here for the first time. In his three previous appearances, he never made it out of the round-robin stage. His greatest triumph to date was winning the Masters 1000 crown at Indian Wells in March. He's also finished runner-up to Nadal the past two years at Roland Garros, so is no stranger in competing on the grandest of stages.
“This is just a big, big dream come true for me,” Thiem said. “It’s one of the best tournaments all year, one of the most prestigious tournaments all year, and I’m getting the chance to play in the final. It’s unreal. To beat the defending champion today, a great player, is an unbelievable achievement.”
Thiem leads Tsitsipas in their head-to-head series, 4-2. They’ve only played once in 2019, just six weeks ago in the final of the 500-level event in Beijing. There, Tsitsipas led by a set and a break, 6-3, 2-1, before Thiem battled back to win in two hours and 11 minutes with a 3-6, 6-4, 6-1 victory. The two combined for 58 net approaches in 169 points in that match.
“I think today I never went so much to the net in one match before,” Theim said afterwards. “It’s the right thing to do. I think it’s very important to shorten up the points, to finish points at the net.”
“I was so close. I was one point from getting another break and serving for it,” Tsitsipas said that day. “I did the wrong thing. I went back, took some time, and he played smart. He serve and volleyed.”
Thiem has won three of their four hard-court meetings. This will be their first on indoor hard courts.