Rafael Nadal will have to wait another year to win the ATP Finals.
The world No. 1 withdrew from the elite, season-ending tournament after losing his opening match to David Goffin 7-6 (5), 6-7 (4), 6-4 on Monday at the O2 Arena.
Nadal pulled out of the Paris Masters at the quarter-final stage 10 days ago and admitted ahead of the ATP Finals on the indoor hard-court he struggles on, that his knees, which have caused him trouble throughout his career, were still "not perfect."
Despite having qualified 13 consecutive times for the ATP Finals and eight appearances, Nadal has never won the event.
Goffin claimed an ugly opening set via a tiebreak and was on the verge of victory in the second, but Nadal's fighting spirit saved four match points to force another tiebreaker and draw level.
However, the third set proved a step too far for the 16-time Grand Slam champion, who began to struggle with his movement and was in visible pain as Goffin finally claimed victory.
Nadal ominously waved goodbye as he left the court, and confirmed his withdrawal shortly afterward.
Dimitrov wins in debut
Making his debut at the ATP Finals earlier, Grigor Dimitrov withstood a comeback attempt from Dominic Thiem and held on for a 6-3, 5-7, 7-5 victory.
The sixth-ranked Dimitrov maintained his focus despite being narrowly denied a chance to serve out the match in the second set, and then being broken at his first chance in the third.
"Every year you learn more about yourself, about the game, about the players," Dimitrov said. "I've done also a lot of work on and off the court. It's finally starting to kind of, like, come together."
Having become the first player from Bulgaria to qualify for the event, Dimitrov quickly settled into his new surroundings.
It was Thiem, who made his debut at the event last year, who started nervously, allowing Dimitrov to ease to the opening set.
"There's always a little bit of tension before every match. And especially here, of course, a little bit because of all the atmosphere, arena," Thiem said. "Also because it's your first match, it's against a really, really good opponent, so you're very tense."
Facing break point at 5-5 in the second, Thiem produced a forehand winner to deny Dimitrov an opportunity to serve for the match, and then broke to love in the following game to level.
Dimitrov broke in the seventh game of the decider to take control once more. However, as he attempted to the serve out the match his poise deserted him and a wayward backhand made it 5-5.
In the pair's most recent meeting, in Madrid, Thiem won after saving five match points and it appeared another remarkable escape might be on the cards.
But rather than Dimitrov, Thiem it was who wilted. The No. 4-ranked player produced two double faults from 0-30 down to give his opponent another chance to close the show, which this time he took.
"To be honest, I didn't think that much about that last match against him. I thought about my last match against John [Isner] in Paris," said Dimitrov, referring to another recent loss in which he wasted a match point.
"It was kind of a similar situation. I was like, 'Not again, definitely not again,"' he added with a smile.