Juan Martin del Potro got his ATP World Tour Finals campaign off to a winning start as he defeated Richard Gasquet 6-7 6-3 7-5 at London's O2 Arena.
Victory comes 48 hours after Del Potro's preparation for his fourth appearance at the season's ending tour finals were disrupted by his suitcase and passport being stolen on route from the Paris Masters.
Gasquet had earlier surged ahead despite missing the opportunity to win the opening set when broken by Del Potro in the ninth game but the Frenchman soon recovered to lead after prevailing 7-4 in the resulting tiebreak.
But the world No.9 produced 13 unforced errors in the first five games of the second set to hand Del Potro the initiative and opportunity to square the match which he duly took, despite passing up two early set points, with just short of an hour and a half on the clock.
Neither player looked like giving an inch in the opening exchanges of the third set but it was Gasquet who blinked first, netting a backhand as Del Potro converted his third break-point chance of the seventh game but the Argentine failed to serve out the match as the US Open semi-finalist rallied.
Del Potro then took the second of two break chances in the very next game and made no mistake when faced with serving out the match at the second time of asking to end an enthralling contest on the opening day of the climax to the ATP season.
With defending champion Novak Djokovic and six-time winner Roger Federer for company in Group B, Del Potro's task of reaching the last four remains a tough one while Gasquet's position in his first tour finals since 2007 is perilous.
"Hopefully I can beat them [Djokovic and Federer] but it's going to be really tough for me," Del Potro said. "I don't have anything to lose against them.
"Richard has an unbelievable backhand and he is a good fighter. This tournament means a lot to me. In the end, I played solid."
Gasquet added: "I think I took a little confidence after this match.Of course, I'm a little bit disappointed because I was really close to winning.
"It was important for me to win the first match. Now I need to play two big players again, so it's very difficult. The level is very high, so every match is a final for me."
Stanislas Wawrinka earlier took a giant step towards the last four with victory on his first ATP World Tour Finals appearance against Tomas Berdych in three sets.
The Swiss had won five of the previous six meetings and took little time to assert his authority, taking the opening set 6-3 as Berdych served three double faults.
But the former Wimbledon finalist, in his fourth appearance at the season ending finals drew on his reserves and after Wawrinka had salvaged a tie-break, the Czech took it 7-0 with a barrage of forehands.
Wawrinka could easily have folded on his O2 Arena debut but is a reborn force in the top eight and broke Berdych twice in the final set as his second serve faltered, to claim victory on day one in the English capital.
"I enjoyed it [tour finals debut] a lot especially with the victory here today," said Wawrinka, who calmed fears over an ankle injury which he received treatment for in the third set.
"My first impression was really, really nice I've only ever seen the tournament on TV so to play here was something different. My first match was really special.
"It'd always nice to play in London, they've such nice people. There was a bit of Swiss support so that was really, really nice.
"This is more about myself and my career, I'm really proud to be here. I've had a great year and I'm not trying to compare myself to Roger. I've got to try and be closer to him and maybe that should be my goal."
Berdych who must now beat David Ferrer or Rafael Nadal to stand any chance of reaching the semi-final for just the second time, said: "It's about choosing the right shot at the right moment and that's what Stan was doing better today. It's been about a few points and he did better today.
"The opponents, especially on paper, look even tougher. It's not going to be easy at all; there is no easy match from this tournament, defiantly not. Whoever it's going to be next, I'm just going to try to prepare for that, and then go step by step really.
"I've been here in a couple of situations which doesn't look good at all and then I was able to go through the group. So I really just have to go one by one."
In the doubles competition, eighth seeds Mariusz Fyrstenberg and Marcin Matkowski sprung a surprising by defeating Aisam-Ul-Haq Qureshi and Jean-Julien Rojer in straight sets.
The evening's all-Spanish doubles encounter saw David Marrero and Fernando Verdasco secure a seventh successive win against fourth seeds Marcel Granollers and Marc Lopez in straight sets.