Dominic Thiem still has a chance to reach the semifinals at the ATP Finals after beating Kei Nishikori 6-1, 6-4 Thursday.
Thiem, who lost both of his previous matches at the season-ending tournament, needed to win in straight sets to have any chance of advancing.
Six-time champion Roger Federer, however, needs only to win one set in the late match against Kevin Anderson to advance alongside the South African. If Anderson wins in straight sets, second place will be decided by who has won a higher percentage of games.
Thiem broke twice in the first set against Nishikori, who won only one game in his previous match against Anderson.
Earlier on Wednesday late night, Marin Cilic keeps his hope alive of making into the semifinals of season ending ATP Finals after former US Open champ Croat beat John Isner 6-7 (2/7), 6-3, 6-4 in ednesday's second match.
The Croatian fifth seed had lost nine of his previous 10 matches at the Finals, and he looked in danger of another letdown when he dropped the first set against Isner.
But Cilic, whose only other Finals victory came against Kei Nishikori in 2016, had other ideas as he roared back to take the final two sets.
"I started to feel the ball really well in the second set. I was playing great tennis towards the end," Cilic said.
Cilic's revival keeps him in with a chance of qualifying for the semi-finals, while American eighth seed Isner still has an outside chance of advancing despite losing his first two matches.