Russia's Andrey Rublev admitted he had to raise his game to reach the semi-finals of the ATP grass court tournament in Halle by beating 2011 champions Philipp Kohlschreiber on Friday.

Rublev is the last remaining seed in the Halle draw after Roger Federer and world number two Daniil Medvedev were among the big-name casualties in the early rounds.

The 23-year-old Russian held his nerve in the first set tie-breaker to earn a 7-6(4), 6-2 quarter-final win over Kohlschreiber to reach his sixth semi-final of 2021 on ATP tour.

"I am happy with my performance to reach the semi-finals for the first time (in Halle)," said Rublev.

"The first set was really tough. He was 3-0 up in the tie-break and I came back, which was the key.

"After the first set, I think he mentally went down and I was pumped up."

On Saturday, world number seven Rublev, will face Georgian qualifier Nikoloz Basilashvili, currently 30th in the world, who later beat Lloyd Harris of South Africa 6-4, 7-6 (7/5) in their quarter-final on Friday.