Home favourite Jannik Sinner began his ATP Finals title defence by defeating a physically hampered Felix Auger-Aliassime 7-5, 6-1 in Turin.
The second-seed Italian, who is challenging Carlos Alcaraz for the year-end world number one ranking, was superb on serve throughout the high-quality first set.
However, the momentum shifted when the eighth-seed Auger-Aliassime injured his left calf late in the first set, severely limiting his movement and resulting in him winning just one game in the second set.
The win puts Sinner, who has now won 27 consecutive matches on indoor hard courts, top of the Bjorn Borg Group.
In the Jimmy Connors Group, American Taylor Fritz opened with a solid 6-3, 6-4 victory over Italy’s Lorenzo Musetti.
