Roger Federer began his quest for a fifth end-of-season championship with a straight-sets win over Spain's David Ferrer in London.
The 29-year-old Swiss took his career record against Ferrer to 11-0 with a 6-1 6-4 victory in his opening match at the ATP World Tour Finals.
Federer joins Andy Murray, who earlier beat Robin Soderling, at the top of Group B and the pair will meet on Tuesday in their second round-robin match.
It would have taken a brave person to predict Ferrer prevailing on Sunday evening against the four-time champion, making his ninth successive appearance at the year-end championships.
However, despite the incredible list of accomplishments, Federer has displayed signs of vulnerability since winning his 16th Grand Slam title in Australia back in January.
He failed to reach another major final in 2010 and, perhaps even more surprisingly, let match points slip away in four matches, the last of which came in Paris last week when the world number two missed five match points before losing to France's Gael Monfils.
If Federer needed a confidence boost in London then he merely had to look at his 10-0 head-to-head record against Ferrer, whose relentless energy and commitment had never seriously troubled him before.
The indoor setting was also to Federer's advantage, although the slow conditions had been compared to Valencia where Ferrer picked up the title earlier this month.
Federer certainly looked the more comfortable after receiving a raucous welcome from the 17,500 spectators inside the O2 Arena, storming into a 4-0 lead as Ferrer struggled desperately to keep pace, but the Swiss then handed back one of his breaks by dropping serve from 40-0 in game five.
The chances of the Spaniard winning the set remained remote at 4-1 down and they disappeared completely when he was broken for the third time in a lengthy sixth game, allowing Federer to serve out the set comfortably.
Lacking the power to hit through the world number two, Ferrer needed to keep his man on the back foot somehow, but serving at around the 50% mark meant cheap points were few and far between and Federer was too often able to dictate.
There were two chances for the Swiss to move ahead early in the second set before Ferrer blazed a forehand wide on the third, and leading by a set and a break there seemed to be nothing standing between Federer and an early night.
Ferrer is nothing if not fully committed, however, and, backed by a crowd wanting to see a lengthy contest, the 28-year-old played his best game of the match at 3-2 down but still came up short as Federer found his first serve to see off two break points.
It was not vintage Federer - 26 unforced errors were evidence of that - and there was another lapse of concentration before he saw off three break points in serving out the victory after one hour and 20 minutes.
BBC Sport
