Alexander Zverev snapped back into focus after a mental swoon to reach the semi-final of the new Koln ATP event as he beat Lloyd Harris 6-4, 3-6, 6-0 on Friday.
The seventh-ranked German was well in command 6-4, 1-0, when his game suddenly went walkabout with the loss of his next four service games.
But Zverev regained control to halt the slide, taking the quarter-final into a deciding third set and turning the tide against his tiring South African opponent.
Harris, January’s Adelaide finalist, was bothered by a right upper leg injury on his way to defeat
Zverev can see there is room for improvement in his form: “I have got to do a better job of keeping my focus until the end of a match.
“I relaxed a little bit and then he picked up his game,” the winner said. “You only have great players on the Tour.
“Once you lose your focus, it doesn’t matter what your ranking is, it doesn’t matter how many titles you won, you have still got to play until the end otherwise it can go the other way very quickly.”
Zverev is hoping to break through for a first title this season after reaching the US Open final against Dominic Thiem.
Qualifier Harris was tapped out as he played his fifth match of the week in this Rhine-side northern German city.
“(He) came through qualifying, so he had a lot of matches under his belt already,” Zverev said. “He’s playing with a lot of confidence.
Zverev next faces Alejandro Davidovich Fokina after the Spaniard defeated Austrian Dennis Novak 6-3, 2-6, 6-3.