Novak Djokovic booked his place in the Astana Open final in Kazakhstan where he will face Stefanos Tsitsipas after Daniil Medvedev retired injured with the semi-final level at one set apiece 4-6 7-6 (8-6).
Having won the opening set 6-4, Russia's Medvedev carved out match point in the second set, only to go on to lose it in a tie-break to Djokovic.
Medvedev then surprisingly retired injured from the clash before the third set could begin, allowing Djokovic to progress to the final.
Djokovic said in his on-court interview as quoted by Sports Central: "He [Medvedev] told me he pulled an adductor in his leg. "I know Daniil, he's a great guy, he's a fighter, he's a big competitor. He wouldn't retire a match if he didn't feel that he [could] continue or [if it wouldn't] worsen his injury.
He added: "It was such a close match, particularly in the second set. I would probably say he was a better player on the court in both sets. I was fighting and trying to find a way. "I found a way to win the second, but I'm just sad for the tournament and for these people who were enjoying the battle, and for Daniil that it had to end this way.
Djokovic will now aim to seal back-to-back titles in Sunday's final against Tsitsipas, who was a 4-6 6-4 6-3 winner against Andrey Rublev. The Serbian, who lifted his 89th tour-level crown in Tel Aviv last week, leads Tsitsipas 7-2 in their ATP head-to-heads.
Medvedev explained: "It's the second time in my life I retired like this with a pulled muscle. "So here, on the second point of the tie-break, I felt a little strange pop in my adductor. I first thought maybe it's a cramp and after the point I was like: 'No, probably not a cramp.' "And during the tie-break, I felt I can play like five, 10 more points but that's it. If I play one more set, you can do it, but you can probably miss half a year instead of one month.
There will be an all-American final at the Japan Open in Tokyo after Taylor Fritz and Frances Tiafoe won tight tussles on Saturday.
Fritz only just made it to Japan in time for his first match after a week in Covid quarantine in Korea but he continued his progress with a 6-3 6-7 (5-7) 6-3 victory over Denis Shapovalov, which guaranteed he will make his top-10 debut next week.
Fritz said: "It's pretty amazing what I've been able to accomplish this week. Just from thinking that I might not even be able to play this tournament to then seven days in a room, wake up at 5am, take a flight here and just show up and play. It's pretty crazy how quick things happen. It was only four days ago.
Tiafoe has carried his excellent form into the Asian swing and overcame a major second-set blip to defeat South Korean Kwon Soonwoo 6-2 0-6 6-4.
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