Defending champion Jannik Sinner attributed his straight-set victory over Ben Shelton in the penultimate group match of the ATP Finals to his mental strength.
The Italian, who had already secured top spot in Bjorn Borg Group after winning his opening two matches, triumphed 6-3 7-6 (7-3) to advance to the knockout stages without dropping a set or losing a service game.
The 24-year-old has not lost a match since being forced to retire because of cramp from his third-round match at October's Shanghai Masters, winning titles in Vienna and Paris along the way, while his most recent indoor defeat came at this tournament in 2023.