Novak Djokovic recovered from a wobbly start to defeat debutant Casper Ruud in his opening group match at the ATP Finals in Turin on Monday.
The world number one is bidding for a record-equalling sixth title at the season-ending tournament but has not lifted the trophy since 2015.
He arrived in Italy on the back of a 37th Masters title in Paris and kept his winning run going with a 7-6 (7-4), 6-2 victory over Ruud, who is the first Norwegian to qualify for the tournament.
Djokovic dropped serve in the opening game after a point when he stumbled and dropped his racket before netting, but he settled into the match and broke back for 3-3.
Ruud, who has developed his game this year to be a threat on all surfaces, rather than just his favoured clay, did well to save two set points at 4-5, but Djokovic came out on top in the tie-break.
The second set was a masterclass from Djokovic, who applied intense pressure to his 22-year-old opponent’s serve and eased to victory.
Stefanos Tsitsipas of Greece faces Russia’s Andrey Rublev later Monday.