Basel - Jan-Lennard Struff ended the possibility of a rematch between Roger Federer and his US Open conqueror John Millman by beating the Australian at the Swiss Indoors on Tuesday.
The 52nd-ranked Struff won 7-6 (7/3), 6-2, with Federer opening his bid for a ninth title in Basel later in the day against Serbia's Filip Krajinovic.
The 20-time Grand Slam winner revealed earlier this week that he had been struggling with a hand injury since the grass-court season.
The local hero, who was once a ballboy at the event, stands 66-9 at the St Jakobshalle and has reached the final in his last 11 appearances.
Federer last lost in 2013, going down to Juan Martin del Potro.
"Playing Federer here is tough," said Struff.
"I will watch the match with my team and we will try and see what we can do.
"It won't be easy for sure."
Seventh seed Daniil Medvedev, a semi-finalist last week in Moscow, saw off German Maximilian Marterer 6-3, 7-5.
Russian Medvedev stands at a career-high ranking of 20th, with three titles this season and will next face Andreas Seppi after the Italian defeated Japan's Taro Daniel 6-0, 6-4.
Results from the Swiss Indoors ATP tournament in Basel on Tuesday (x denotes seeding):
Jan-Lennard Struff (GER) bt John Millman (AUS) 7-6 (7/3), 6-2
Peter Gojowczyk (GER) bt Nicolas Jarry (CHI) 1-6, 7-5, 6-3
Andreas Seppi (ITA) bt Taro Daniel (JPN) 6-0, 6-4
Daniil Medvedev (RUS x7) bt Maximilian Marterer (GER) 6-3, 7-5
Alexei Popyrin (AUS) bt Matthew Ebden (AUS) 7-6 (7/4), 6-4
Roger Federer (SUI x1) bt Filip Krajinovic (SRB) 6-2, 4-6, 6-4
Gilles Simon (FRA) bt Leonardo Mayer (ARG) 6-3, 6-3