Austria's Dominic Thiem revived his hopes at the ATP World Tour Finals with victory over Frenchman Gael Monfils in London.
Thiem, 23, won 6-3 1-6 6-4 and will go into his final group match against Milos Raonic on Thursday with a chance to reach the semi-finals.
Raonic takes on five-time champion Novak Djokovic in Tuesday's evening session at 20:00 GMT.
Both men have the chance to become the first semi-finalist at the O2 Arena.
| Ivan Lendl Group qualification scenarios (Tuesday): |
|---|
| Djokovic qualifies if he defeats Raonic |
| Raonic qualifies if he defeats Djokovic in two sets |
| Key info: Group tables, results, schedule and BBC coverage |
Thiem became the youngest man since Djokovic in 2009 to win a match at the ATP finale, and the first Austrian to do so since Thomas Muster in 1996.