Medvedev, 27, will face on Saturday for a place in the final the Bulgarian Grigor Dimitrov, 28th in the world, who fell earlier in the day from Australian Alex De Minaur.
Quickly broken and author of numerous unforced errors, Auger-Aliassime had a nightmarish first set.
More eye-catching then but still dominated from the baseline, the native of Montreal (22 years old) did not find the key against an opponent who is slowly becoming his pet peeve.
In five confrontations, it is always the Russian who has won.
Faced with De Minaur (24, 25th at ATP), Dimitrov was the most solid in the long exchanges at the end of the match.
Broken from the start of the decisive round, the Bulgarian used his experience to overthrow an opponent who had committed too many unprovoked faults.
He also had very strong nerves during the final decisive game: trailing 0-3 then 4-6, the rock of Haskovo saved two match points to finally win after a last exchange where he was put struggling before a genius forehand.
© 2023 AFP