Novak Djokovic remained stunned on Saturday as Daniil Medvedev made a sudden withdrawal after two semi-final sets to send the Serb into the final at the ATP event in Kazakhstan 4-6, 7-6(4).

Medvedev won the opening set in the battle of former No. 1 players and was only narrowly out-hit in the second set which ended in a tiebreak win for Djokovic.

But seconds after dropping the set, a good natured Medvedev walked up to his opponent at the net and announced he could not go on.

“He told me that he pulled the adductor muscle on his leg,” Djokovic said as he moved into a Sunday final in Astana against Greek Stefanos Tsitsipas, who beat Andrey Rublev in a 4-6, 6-4, 6-3 fightback.

The final will be a repeat of the Rome title match won by the Serb.

“I’m still surprised that he retired from the match,” Djokovic said.

“He looked completely fine – maybe the last seven or eight points I saw him move maybe slightly slower – but it’s a shock. 

“I couldn’t penetrate through him. He was a wall, 

“Honestly I was ready for a three set battle. I really hope his injury is not that serious.”

Djokovic added: “Daniil is a big fighter, a big competitor. He would not retire unless he felt he wouldn’t continue or that he would make his injury worse.

“”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 advanced in just under two hours with 27 winners and 25 unforced errors; Medvedev’s numbers were 26 and 11.

The winner will be seeking his second title in eight days after winning the trophy last weekend in Israel.