ASTANA, Kazakhstan -- Novak Djokovic didn't play as well in his Astana Open quarterfinal on Friday as he did in the first two rounds.
"Still, it was enough," Djokovic said after beating Karen Khachanov 6-4, 6-3.
"I managed to produce some good tennis when it was the most needed."
Djokovic conceded a 3-0 lead but broke Khachanov for the first set with a backhand volley. He broke Khachanov for 3-1 in the second and finished their quarterfinal with an ace.
Daniil Medvedev awaits in the semifinals. Medvedev has a 4-6 win-loss record against Djokovic, and they haven't met since the Paris final last November, when Djokovic won in three sets.
"I thought about it before the (quarterfinal) and we have only played one tournament together this year, which was Roland Garros," Medvedev said. "This is the second one and we meet again and I am really happy."
Medvedev was too consistent and good for Roberto Bautista Agut 6-1, 6-1. Bautista Agut went in with 4-1 record against Medvedev but was blown away.
"It is not easy to play against Roberto. I tried to mix it up and surprise him a little bit and it worked very well."
Tsitsipas hasn't dropped serve this week after saving five set points in the tiebreaker against Hubert Hurkacz.
"Most of those situations, I was not the fortunate one serving," Tsitsipas said of the set points. "I was still able to break through and get back fighting, and it was very, very emotional to get that first tiebreak after having thrown my body on the court."
Tsitsipas prevailed 7-6 (8), 6-3 to reach his ninth semifinal this year.
Rublev took care of Adrian Mannarino of France 6-1, 6-2.