Novak Djokovic's fate in the ATP Finals hangs in the balance despite his win over Hubert Hurkacz on Thursday.
Djokovic defeated Poland's Hurkacz, a replacement for the injured Stefanos Tsitsipas, 7-6 (7-1) 4-6 6-1 in Turin.
However, the world number one will not qualify for the semi-finals if Holger Rune beats Jannik Sinner in the final group game later on Thursday.
Italy's Sinner, who ended Djokovic's 19-match winning streak on Tuesday, is guaranteed a place in the last four.
The 22-year-old home favourite, who will finish at least second in the Green Group, is set to become the first Italian to play in the semi-finals of the season-ending tournament.