Novak Djokovic was down early, but not out, while Roger Federer also bounced back from a slow start and is back in the title match of the ATP World Tour Finals.

Djokovic, already assured of the season-ending world No. 1 ranking, fought back from a set and a break down to earn a 4-6, 6-3, 6-2 win over Juan Martin del Potro in the first semifinal.

Federer, who has won the season-ending tournament each of the last two years, rebounded after being down a break to Andy Murray in the first set, then rolled in the second to earn a 7-6 (7-5), 6-2 victory.

Monday's final will match the top two players in the world, as Federer tries to win the season-ending event for the seventh time overall and Djokovic goes after the crown for the second time.

Federer will be trying for a bit of history on Monday. He will be gunning for his 77th career title, which would tie him with John McEnroe for third on the all-time list. Only Jimmy Connors (109) and Ivan Lendl (94) have won more titles in the Open Era (1968).

The Swiss superstar, who has already won six titles in 2012, will also be trying to become the first man since Lendl in 1987 to win the season-ending tourney three straight years.

Djokovic, meanwhile, won this tournament in 2008 and will be trying for his 34th career title. He is 5-5 in finals in 2012.

The Serb, who lost to del Potro in the bronze medal match at the London Olympics in July, nearly didn't make it to the final after a slow start Sunday.

Del Potro picked up the first break of serve on Sunday for a 5-4 lead and held at love to close out the first set. He then broke for a 2-1 lead in the second, ending a rally of more than 20 shots with a blistering forehand down the line that Djokovic could not return.

Djokovic quickly broke back, finally converting on his fourth chance of the game and sixth of the match. The tide then appeared to turn, as he broke again to force a third set.

It was all Djokovic in the third. He broke for a 2-1 lead and broke again for 5-2 before holding at love to win it. The Serbian star won all but two of his service points in the dominating third set, capturing 27 of the 40 total points played.

"He deserved to win today," said del Potro about Djokovic. "I think I played really good in the first two sets. If you don't play (for the) whole match (at) your best level, it's really difficult to beat him."

Federer won a tight first set Sunday that featured a break for each. He then converted the only two break opportunities for either man in a dominant second set. Much like Djokovic, Federer won 16-of-18 points while serving in the second set.

Murray and Federer met for the fifth time this year. Federer won three times to improve to 9-10 lifetime against the Scot. He won his 17th career Grand Slam championship by beating Murray in the Wimbledon finale, but Murray rebounded a few weeks later to beat Federer for the gold medal in the Olympics.

Federer owns a 16-12 lifetime mark against Djokovic. The two have split four meetings this year, with Federer taking the most recent two.