Alexander Zverev sent over an eighth ace on match point to mark his return to a semi-final after last year’s ankle injury, with the German defeating Lorenzo Sonego 7-5, 6-4 on Thursday in Dubai.
The seventh seed will play in the final four for the first time since he was stretchered off court at Roland Garros after rolling his ankle and tearing ligaments against Rafael Nadal last June.
The Tokyo Olympic champion missed the second half of last season as he took months to heal and rehab.
Zverev advanced in just under two hours against his unseeded Italian opponent.
“It’s been very difficult the past nine months,” the winner said. “I didn’t play tennis for the longest period of my life.
“But this shows the hard work pays off. I’m extremely happy with the progress and how I’m playing.”
Zverev saved all six break points he faced while breaking Sonego twice. Victory pulled him level this season, 5-5 in match play.