Both men have enjoyed career-defining weeks with each player having claimed wins over Roger Federer and defending champion Alexander Zverev as well as Thiem defeating Novak Djokovic on their way to identical 3-1 records.
Tsitsipas' road to the final
The Greek began his week with his first career victory over world number four Daniil Medvedev by a 7-6 (5), 6-4 scoreline. He then clinched his semifinal berth with a sterling 6-3, 6-2 thrashing of Zverev and concluded round-robin play by getting edged out by Rafael Nadal 6-7 (4), 6-4, 7-5. In the semifinals, Tsitsipas outclassed Federer 6-3, 6-4.
Thiem's road to the final
The Austrian opened the tournament by knocking off Federer 7-5, 7-5, his fifth consecutive win over the six-time ATP Finals champion. He then proceeded to stun Djokovic 6-7 (5), 6-3, 7-6 (5), rallying from a 4-1 deficit in the third set tiebreaker. He finished up round-robin action with a 7-6 (3), 6-3 loss to Matteo Berrettini. Thiem dethroned Zverev 7-5, 6-3 in the semifinals.
Thiem leads the head-to-head matchup 4-2 including having won their last meeting in the Beijing final in which the Austrian rallied from a set down to take home his fifth title of the season. Tsitsipas last knocked off Thiem in the third round of the 2018 Canadian Open, where he reached the final. This is their fifth career matchup on a hard court.
Who will win?
Both players are performing at a very high level and each man possesses a ton of firepower. It seems that Thiem is using the quick courts to his advantage, his forehand looking as hard and flat.
This is the first ATP Finals title match to feature two one-handed backhands since 1996 and while Thiem relies on power, Tsitsipas will use placement as his greatest asset, especially crosscourt.
The edge on serve goes to Thiem as he has been getting in a high percentage of serves throughout the tournament. He also has served well when he has needed to, but fatigue could play a factor as the fifth seed has had a couple of long matches whereas Tsitsipas has breezed through four of his five contests.
Despite most of the advantages seeming to be in Thiem's favor, Tsitsipas is the pick because he will be the fresher of the two and while both players will be clearly nervous playing in the biggest final of their careers, the Greek will ultimately prevail and collect the fourth - and largest title of his career to cap a spectacular week in London.
Prediction: Tsitsipas in three sets