Russia’s Daniil Medvedev stunned the world No 1 and defending champion, Novak Djokovic, in the Western and Southern Open semi-finals on Saturday.

The No 9 seed dramatically stepped up his game after losing the first set in Cincinnati, eventually prevailing 3-6 6-3 6-3 to set up an unexpected final against David Goffin.

After losing the first set, Medvedev decided he had nothing to lose midway through the second, becoming more aggressive in his play, particularly on second serve. It changed the complexion of the match, as the previously dominant Djokovic suddenly looked vulnerable.

“I was so tired in the first set and playing Novak, I thought I’m not going to be able to keep the intensity,” world No 8 Medvedev said in a courtside interview with ESPN. “Then there was one momentum change in the second, and I just started playing unbelievable.”

At three games all in the second set and 0-30 down on serve, Medvedev begin powering down second serves to reel off four successive points, including a second-serve ace, before breaking Djokovic in the next game with a down-the-line winner.

Medvedev never looked back and he was delighted to win a match he acknowledged would often have slipped away in the past. “Many [other] matches like this I would go crazy and break the racket and lose 6-3 6-3,” he said.

The 23-year-old from Moscow followed up victory over Djokovic at Monte Carlo in April, and reached his third successive ATP Tour final, having lost to Nick Kyrgios in Washington and Rafael Nadal in Montreal.

Djokovic will now turn his attention to the US Open, which begins on 26 August – and the Serb was full of praise for his opponent.

“I did not experience this too many times in my career that someone goes so big on second serves, and basically just plays two first serves for an extended period of time,” Djokovic said.

“When someone serves a 128mph second serve and goes for every shot, you just have to congratulate him … he played amazing tennis from 4-3 in the second set. Not much that I could really do. [Daniil] is working his way to the top five. Today I did lose a tennis match, but I didn’t do too much wrong.”

Medvedev, who also beat Djokovic at Monte Carlo in April, will play Belgium’s David Goffin in the final on Sunday, with the winner set to claim their first-ever Masters title. No 16 seed Goffin beat France’s Richard Gasquet 6-3 6-4 in the earlier semi-final.

“I’m really happy,” Goffin said afterwards. “I’ve played the best tennis here in the past few years ... It’s a great moment for me.” The Belgian also benefited from a walkover in his quarter-final against Yoshihito Nishioka. “It was almost a day off, so I was fresh and physically 100% today to play against Richard”.

Goffin surged to an early 4-1 lead with a backhand winner down the line to break, before closing out the first set. Gasquet grabbed a 2-0 lead in the second, but Goffin struck back to win five of the next six games – and sealed victory when the Frenchman sent a backhand long.

The women’s final also has an unexpected line-up, with Madison Keys set to take on wildcard Svetlana Kuznetsova. The Russian is ranked outside the world’s top 100 but has enjoyed a fine run of form in Ohio, beating Ashleigh Barty in the semi-final to deny the Australian the world No 1 ranking.