LONDON – Near defeat, Daniil Medvedev suddenly changed tactics in the ATP Finals and claimed the biggest title of his career by beating US Open champion Dominic Thiem 4-6, 7-6 (2), 6-4 on Sunday. Medvedev, ranked fourth, became the first player to beat each of the men who ranked 1-3 in the season-ending championship, and only the fourth to do so at any tour event in the last 30 years.

The comeback against No. 3 Thiem, which lasted more than 2 1/2 hours, added to the victories Medvedev produced against No. 1 Novak Djokovic in the free-for-all portion of the tournament and against No. 2 Rafael Nadal. in the semifinals on Saturday on an indoor hard court. Viewers were excluded due to the coronavirus pandemic.

Medvedev, 24, was 5-0 overall, a big change from a year ago when he was 0-3 in the ATP Finals. The tournament now ends its 12-year run in London, moving to Turin, Italy, next year.

Russia’s Medvedev closed 2020 with a 10-0 mark in November, including seven victories against members of the Top 10. He had zero victories over Top 10 opponents in the previous 12 months.

Thiem’s ​​defense and power from the baseline put him on top early on, and strong serve at key moments allowed him to save the first eight break points he faced. But Medvedev, Nadal’s runner-up at the 2019 US Open, finally converted in his sixth break opportunity of the third set, and ninth of the match, sneaking up behind a return, making a winning forehand volley and coming up 3-2.

That was enough, because Medvedev never faced a breaking point the rest of the way; finished with 12 aces.

A key change came in the second set tiebreaker, thanks to a change in style from Medvedev.

Thiem had taken a 2-0 lead before Medvedev returned, using an element of surprise by running to the net more often than usual, both behind serves and on returns, and regaining the next seven points. Medvedev continued that strategy to great effect in the final set as well.

It seemed to baffle Thiem, who had won three of the pair’s previous four matches, including in straight sets in the semifinals in New York in September en route to his first Grand Slam trophy. In Sunday’s second set, Thiem had breakout opportunities to take a 4-3 lead, but missed a short shot in one, reacting by putting his hands on his hips, and Medvedev pulled an ace in the other. Thiem stumbled and fell onto the court in the next game, but seemed fine.