MUNICH — Casper Ruud took his time finding his rhythm as he beat Alex Molcan 3-6, 6-4, 6-4 to reach the quarterfinals at the BMW Open on Thursday.

Molcan built a 4-0 lead in the first set as Ruud struggled with his serve, but the clay-court specialist fought his way back and broke Molcan at 4-4 in the decider before serving out the match.

“It was not the best start for me, but I was able to find my rhythm a little more as the match went on,” Ruud said. “[Molcan is] a tough player, and good confidence for me to get these types of wins.”

The 23-year-old Ruud said he was especially pleased to be playing well at the comparatively high altitude of Munich as preparation for similar conditions at the Madrid Open next week.

It was Ruud’s opening match in Munich after getting a first-round bye. At a career-high No. 7, the Norwegian is the highest-ranked player left in the draw after Alexander Zverev‘s surprise loss to 18-year-old Holger Rune on Wednesday.

Ruud will face eighth-seeded Botic van de Zandschulp in the quarterfinals after the Dutch player defeated Egor Gerasimov 6-2, 6-3.

Germany’s Oscar Otte managed the surprise of the day by beating Reilly Opelka of the United States 7-6 (4), 6-2. Opelka had two set points in the first set, but Otte saved them both before taking the set to a tiebreaker.

Otte’s quarterfinal opponent is Alejandro Tabilo, who was leading 6-2, 2-6, 4-1 when Hugo Gaston retired from their second-round match. Otte cruised past Tabilo 6-0, 6-3 when they played last week at the Serbia Open.