Halle Open
In 2021 Halle Open where he was seeded 5th, he lost in the second round to Félix Auger-Aliassime. Federer was playing against the 20-year-old for the first time. Their 19 years age difference was the biggest in Federer's 1,521 career matches. This was the earliest exit at this tournament for Federer who was seeking his 70th match win in Halle, and his 18th quarterfinal at this event in as many appearances.