The Serb survived a three-set tussle with his Russian rival in Turin

Novak Djokovic came through a three-set battle with Daniil Medvedev at the ATP Finals in Turin, although the grueling nature of the contest was less than ideal for the Serb ahead of the semifinals of the tournament in less than 24 hours' time.

Already guaranteed of a place in the last four of the season-ending event after winning his opening two round-robin matches this week, Djokovic ensured he finished the group stage with a perfect record with his 6-3 6-7 (5-7) 7-6 (7-2) victory over Medvedev on Friday.

But a brutal tug-of-war which lasted more than three hours was perhaps far from perfect preparation for Djokovic before he plays America's Taylor Fritz in the semifinals at the Pala Alpitour on Saturday.

Fritz will be much better rested after sealing his place in the knockout stages with victory over Canada's Felix Auger-Aliassime on Thursday.

Having already seen his own semifinal chances end with two group-stage defeats, Medvedev was largely playing for pride against Djokovic.

But the Russian had a comeback win in his sights when serving for the match at 5-4 in the third set, after breaking Djokovic's serve in a titanic 15-minute game.

But just as he had done against Stefanos Tsitsipas earlier in the week, Medvedev let the opportunity slip as Djokovic broke back to level at 5-5, before going on to exert control in the tiebreak.

Djokovic remains on course for a sixth ATP Finals title - which would equal Roger Federer's record but would be a first since 2015 for the Serb.

Medvedev, who was tournament champion in 2020 and a beaten finalist last year, leaves Turin winless in his three matches, but very much having played his part in an enthralling 'Red Group'.

"Daniil and I have had some battles in the past and I knew coming into the match today that it was going to be his last match of the season and he wouldn't want to finish with a loss," Djokovic said of the thriller in Turin, as he improved to 8-4 in his head-to-head record with Medvedev. 

"Being able to find the last drop of energy to come back into the match. At 4-5 I managed to read his serve and anticipate well and got myself in a good position. I started off very well in the tiebreak.

"Tough three matches for him, losing 7-6 in the third in all three matches. It is not easy, but he is an amazing player. I have a lot of respect for him and what a great battle."

Later on Friday, the last semifinal place will be decided when Russia's Andrey Rublev takes on Greece's Tsitsipas, with both men on one win from their two group matches thus far.

The 'Green Group' wrapped up on Thursday when America's Fritz defeated Auger-Aliassime to book a semifinal with Djokovic.  

Norwegian Casper Ruud had already ensured his place in the final four, but lost his last group stage match in straight sets against the already-eliminated Rafael Nadal.

The semifinals take place in Turin on Saturday, before the final on Sunday.

Djokovic remains the only man unbeaten at the tournament, and should he clinch the title, the 21-time Grand Slam winner stands to earn a cool $4.74 million payday as undefeated champion.