Marco Reus is expected to miss Borussia Dortmund's final two games of 2015 after sustaining a groin injury.
Reus, 26, suffered the problem in the first half of Sunday's 4-1 victory over Eintracht Frankfurt and has been ruled out of Wednesday's DFB Pokal clash.
Kicker reported on Tuesday that he would also miss Saturday's Bundesliga game against Cologne, but the club's media director, Sascha Fligge, told ESPN FC that Dortmund no longer comment on injuries.
However, BVB boss Thomas Tuchel said: "It's not ruled out but it's unlikely that he'll be fit for Cologne.
"I have a better feeling after talking to Marco. I hope that we escape with no more than a scare."
Reus has suffered a succession of injury problems since hurting his ankle in Germany's final friendly before the 2014 World Cup, and has missed several games with groin issues this season, but Tuchel said: "It's not an old injury, it's just a similar region."
Elsewhere, Dortmund midfielder Ilkay Gundogan has warned that BVB are not on the same level as Bundesliga leaders Bayern Munich.
At the weekend, both teams recorded home wins, and the gap between the league's top two teams remained at five points.
"On paper, that's not too much," Gundogan said of the five-point difference, but he added: "It does not reflect the first seven to ten weeks of the season, during which you could have the impression that Bayern are unbeatable.
"We should not make the mistake to perceive ourselves as challengers to Bayern, and should be delighted to have cemented the second position."
Borussia Dortmund have won 12 of their 16 league games, and are just one short of their 13 wins last season. They have a nine-point advantage on third-placed Hertha Berlin, and are 12 points ahead of Wolfsburg and Borussia Monchengladbach.