Marc Bartra suffered a groin injury during Borussia Dortmund's 5-1 rout of Wolfsburg on Tuesday and is a doubt for their upcoming Bundesliga meeting with Freiburg.
The defender, signed from Barcelona in the off-season, set up the first goal for Raphael Guerreiro with a sublime pass, but was forced off inside a quarter of an hour, to be replaced by Matthias Ginter.
Dortmund made light of his absence as Pierre-Emerick Aubameyang struck twice, with Ousmane Dembele and Lukasz Piszczek adding the others as Thomas Tuchel's men took their goalscoring tally to 17 in three matches.
Next up for BVB are Freiburg at Signal-Iduna Park on Friday, but Tuchel could be without classy centre-back Bartra.
"He has adductor problems, which he noticed for a short while when warming up. Then they disappeared," Tuchel said.
"They came back when he made a pass. I can't say what it is. My Spanish is not good enough to do so. It will be very, very tight for Freiburg."
Guerreiro, usually a left-back by trade, enjoyed a superb evening in the centre of midfield at the Volkswagen Arena, adding two assists to his well-taken opener, and Tuchel says the Portugal international's performances are exactly what he expected.
"It doesn't surprise me because he's just that good at playing football," the coach said.
"He carries a really extraordinary presence and gives us the feeling that he has settled in to the team.
"He's incredibly talented and makes the players around him better. It's a real blessing to have a player like him."