Update (5:25pm ET)
It's only muscle stiffness, according to head coach Julian Nagelsmann (via @iMiaSanMia) — not major, despite the mid-game walk-off, and not expected to affect Thomas Müller's availability for Bayern Munich vs SC Freiburg this Saturday.
Minutes after providing a classy assist for Leon Goretzka, Bayern Munich's maestro Thomas Müller left the pitch and went into the dressing room. Only twenty-five minutes had been played in Bayern Munich’s Champions League tilt against FC Viktoria Plzeň, and Müller's day is done.
Bayern were up 3-0 at the time, but went down to ten men for several minutes until seventeen-year-old Mathys Tel came on in the 28th minute to replace him. Müller had already scored a goal as well, Bayern's second — arriving perfectly-timed at the far post in the 14th minute for a cross whipped in by Kingsley Coman.
Thomas Müller has left the pitch to the dressing room. No substitution yet— Bayern & Germany (@iMiaSanMia) October 12, 2022
There's no word yet on what caused Müller to suddenly leave the field. He did not look to be in notable discomfort as he walked off, but the substitution would appear to indicate that it wasn't possible for the Raumdeuter to continue. It had only been his first game back since COVID-19, and Bayern will hope that it's nothing serious.