Dominic Stricker defeated home favourite Lorenzo Musetti in five tie-break sets to make it two wins from two at the ATP Next Gen Finals and advance to the semi-finals.
The world number 111, who is seeded sixth in Milan following a flurry of withdrawals, defeated Musetti 4-3 (7-5) 4-3 (8-6) 3-4 (9-7) 3-4 (8-6) 4-3 (7-3) in Wednesday's epic match that last two hours and 31 minutes.
Having become the first player in the tournament's history to win three successive tie-breaks in Tuesday's win against Jack Draper, Stricker advances with a match to spare.
Musetti now faces a winner-takes-all showdown with Jack Draper on Thursday after the latter recovered to defeat Tseng Chun-hsin 1-4 4-2 4-3 (7-2) 4-2.
In the Green Group, Francesco Passaro saved three match points to overcome Italian compatriot Matteo Arnaldi 4-3 (9-7) 2-4 3-4 (7-4) 4-3 (7-4) 4-3 (10-8).
In what will go down as one of the all-time great matches in Next Gen history, Passaro triumphed after two hours and 38 minutes to get off the mark with his first victory.
"I am very tired," he said. "It was a really long match and this format I think it is tough and physical.
"For me it was physical today, with the tension as well, I was cramping. It was not easy. I am really happy to win and I will enjoy."
Brandon Nakashima moved to the top of the standings with a 4-1 4-3 (7-2) 4-2 victory against Jiri Lehecka as the third seed made it back-to-back wins at the Allianz Cloud.