Borussia Dortmund have said forward Marco Reus suffered a muscular injury during Tuesday's 3-2 defeat at Werder Bremen that could keep him sidelined for up to one month.
The club's official Twitter account confirmed news of the problem accrued by the Germany international during their DFB Cup round-of-16 loss:
The problem is the latest in a long line of injury issues for Reus, with the forward having missed a succession of key games for the Westfalenstadion club, as well as the last two major international tournaments with Germany.
Reus was enjoying an impressive run of fitness this season, scoring 11 goals and recording six assists in 19 Bundesliga appearances. Dortmund sit third in the Bundesliga and two points behind leaders Bayern Munich at the time of his injury.
The blow means he now looks set to miss Dortmund's UEFA Champions League round-of-16 first leg at home to Paris Saint-Germain on February 18. The Black and Yellows will travel to the Parc des Princes for the return leg on March 11.
Not having the 30-year-old on the field means Dortmund are weaker, as Reus has consistently proved himself as one of European football's most dangerous operators. He's enjoyed a new lease of life under Lucien Favre, too.
Reus has a rare blend of pace, excellent technique and a sharp football brain. Whether operating from the left flank or as a split striker, he is a threat who is able to create space and chances for his team-mates and score goals himself.
The worry for Reus is that other attacking stars will overtake him in the pecking order at Dortmund while he sits on the sidelines. Jadon Sancho, Mario Gotze, Julian Brandt, Thorgan Hazard and new arrival Erling Haaland are all talented operators who thrive in a similar area to the ex-Borussia Monchengladbach star.
Favre will shuffle his plans ahead of Saturday's trip to Bayer Leverkusen, who sit fifth in the Bundesliga and five points below Dortmund.