Novak Djokovic had enough of an edge at the beginning and the end as he beat Stefanos Tsitsipas 6-4, 7-6 (7/4) on Monday in the ATP Finals, a defeat that ended the Greek's hopes of finishing the year at number one.

Djokovic, ranked eighth, is chasing a record-equalling sixth title in the season-ending event, previously known as the Masters Cup, that brings together the season's top eight fit players.

The Serbian broke Tsitsipas in the opening game and was not threatened on his own serve as he took the first set.

Tsitsipas managed the only break point of the second set, in the fourth game, after two Djokovic double faults, but the Serbian steadied and held serve.

In the tie break, the Serbian raced to a 5-1 lead. Tsitsipas delayed the inevitable by taking three points but was wide on Djokovic's first match point.

The loss means the injured Carlos Alcaraz will end 2022 at the top of the rankings, unless Rafael Nadal, who lost his opening match on Sunday, can win the tournament.

Djokovic is tied on five titles in the event with Pete Sampras and Ivan Lendl. Only Roger Federer, on six, has won more.

The two-set victory, put Djokovic top of the Red Group ahead of the day's other winner No. 7 Andrey Rublev of Russia, who beat his compatriot Daniil Medvedev  6-7 (7/9), 6-3, 7-6 (9/7).

Rublev appeared on course to take the first set as he opened up a 4-1 lead.

World number five Medvedev, who was inconsistent all day on his serve, mixing 24 aces with eight double faults, battled back, saving two set points at 5-6, to win the set in a tiebreak.

Rublev rediscovered his rhythm in the second set as Medvedev continued to struggle on his serve.

In the third set tie-break Medvedev saved three match points at 3-6 and then a fourth.

But he was powerless on the fifth match point as Rublev closed out the match, slumping on to his back after two and a half hours on court.

"Peace peace peace is all we need," Rublev wrote on the television camera on court at the end of the match, echoing his call for peace in Ukraine when he won in Dubai in February, just after the Russian invasion.