ATP Finals: Rafael Nadal finishes 2019 as the top player in men's tennis, despite tournament exit (VIDEO)

Despite his exit from the ATP Finals tournament, Spanish powerhouse Rafael Nadal celebrated his tennis year on court in London as he was crowned the ATP's World Number 1 for 2019.

Nadal won his final group match at the ATP Finals at The O2 Arena to give himself a glimmer of a semi-final place, only for defending champion Alexander Zverev's win over Daniil Medvedev to consign the Spanish superstar to an early exit.

But Nadal's year overall saw him finish his campaign on a high, as he was confirmed as the ATP's end-of-year world number 1 and presented with the huge trophy on the court in front of an appreciative London crowd.

Ironically, it was his longtime rival Roger Federer who effectively secured the number 1 spot for Nadal by defeating Novak Djokovic on Thursday night.

But there was doubt that 33-year-old deserved his  place at the top of the standings after another stellar year.

Nadal captured his 12th French Open title at Roland Garros, and added the US Open title later in the year to move to within one Grand Slam tournament of Federer's Grand Slam record.

He also performed strongly in the year's other Grand Slam tournaments, reaching the final of the Australian Open at the start of the year, and the semi-finals at Wimbledon in the summer.

He had hoped to finish his year with victory in London, but headed into the tournament with nagging injury doubts following an abdominal injury that had prevented him from completing a tournament since the US Open in September.

Nadal's end-of-year No. 1 title puts him on the same tally as his longtime rivals Federer and Djokovic, with all three superstars claiming five year-end ATP top spot crowns.

"I think this trophy is the work of the whole year, a great year in all terms," said Nadal.

"This trophy with me is a big personal satisfaction.

"There have been some demoralizing moments this year in terms of physical issues. But super happy for everything.

"The big gap between the first until today, 11 years, is a big thing. I don't know if somebody did it or not, but is something difficult."

Nadal said that he was happy to match the marks set by Djokovic and Federer, but also suggested that he may have had even more No. 1 crowns to take him past all-time leader Pete Sampras (with six) if only he hadn't been plagued by injury at various points throughout his career

"I cannot complain, but at some point I feel that there is a couple of years out there that I have been in a position that I had chances to be the number one and I got injured and I could not fight for it," he said.