Bayern Munich manager Thomas Tuchel said he felt "a little bit jinxed" after centre-back Dayot Upamecano tore his hamstring in Wednesday's 1-0 win over Union Berlin.
Upamecano failed to return to the pitch in the second-half after pulling up sore late in the opening period, with Tuchel saying the France defender had a "hamstring tear".
"With a hamstring tear, we talk about (missing) weeks not days" Tuchel said, revealing "he's already been assessed and we have a diagnosis".
Tuchel told reporters he felt "a little bit jinxed", with fellow first-choice centre-back Kim Min-jae away on Asia Cup duty.
"Of course it's extremely bitter for him personally, but also for us in the form he's in.
"He's almost irreplaceable.
"He was in absolute top form for weeks, also in his ambition, his desire to win, his physicality is outstanding.
"It hurts us a lot."
Tuchel said midfielders Konrad Laimer and Joshua Kimmich were also under injury clouds, saying the club would "wait and see... I'm a little bit more worried about Konnie (Laimer) than I am about Josh."
Bayern's narrow victory, thanks to a second-half goal from Raphael Guerreiro, takes them four points behind league leaders Bayer Leverkusen.
Bayern play away at Augsburg on Saturday.