Top-seeded Alexander Zverev defeated Adrian Mannarino 6-4, 6-7 (5), 6-4 to reach the Cologne Championship semifinals on Friday.
Zverev missed the chance to settle the match when he served at 5-3 in the second set, but eventually prevailed after 2 hours, 40 minutes to move another step closer to his second Cologne title in as many weeks.
The German city is hosting back-to-back ATP competitions that were added to the pandemic-disrupted schedule.
Zverev defeated Felix Auger-Aliassime in the final of the Cologne Indoors last Sunday. They could yet meet again, as the Canadian defeated Yoshihito Nishioka 6-3 6-4 in the last quarterfinal of the second tournament for a semifinal place against the second-seeded Diego Schwartzman.
Schwartzman trailed Alejandro Davidovich Fokina of Spain 2-6, 2-5 but fought back to win 2-6, 7-6 (3), 6-1 earlier Friday.
Zverev next faces Italian wild card Jannik Sinner, who recovered after losing eight games in a row to upset Gilles Simon 6-3, 0-6, 6-4. Sinner was 0-2 down in the deciding set.