Novak Djokovic began his campaign at the ATP World Tour Finals with a 7-6 (7-4) 6-3 victory over Jo-Wilfried Tsonga in London.
The world number one followed the lead of Andy Murray, who had beaten Tomas Berydch in the afternoon session on the opening day, in making a successful start in Group A.
Djokovic - who had last the previous four meetings between the pair on indoor courts - was by no means at his best but was still too strong for the Frenchman, triumphing in one hour and 39 minutes.
Crucially the Serbian took two of the three break point chances he created in a tight tussle, though all of them came in a second set that he dominated.
The first, in contrast, had been much tighter. Indeed, it was Tsonga who seemed to have the upperhand, only for the seventh seed to waste the opportunities that came his way.
He put pressure on during a wobbly opening service game from Djokovic, who had suffered a shock loss at the Paris Masters last week, while break-point opportunities failed to be taken in the seventh and 11th games.
The reigning Australian Open champion staved off the danger at 5-5 with an impressive ace - then piled on the pressure himself at the beginning of the tie-break that he would take at a canter.
With his tail now up, Djokovic looked more dangerous from the off in the second. He immediately registered a break, Tsonga flashing a forehand too long on the run, and then clinched victory on his opponent's serve.
The result sets up a mouth-watering clash between Djokovic and home favourite Murray on Wednesday, with the winner of that tussle knowing he will have one foot in the semi-finals of the end-of-season event at the O2 Arena.