Borussia Dortmund boss Peter Bosz does not know if leading scorer Pierre-Emerick Aubameyang will be available to face Hannover this weekend.
Aubameyang topped the Bundesliga scoring charts last term and has been similarly prolific in 2017-18 to date, with 15 goals in 14 appearances across all competitions.
The Gabon striker was denied the chance to add to that tally during Tuesday's 5-0 DFB Pokal win over Magdeburg after he was sidelined with muscular soreness.
Speaking at a news conference ahead of Saturday's match, Bosz confirmed Aubameyang's injury had not completely subsided.
"Mario Gotze is fit to play, but I have to wait and see about Christian Pulisic (calf) and Aubameyang," he said.
"We will go to the facilities and see how Auba is doing. If it is necessary [to replace him] we will see.
"It's very hard to beat Hannover. They are a good team with good organisation."
Alexander Isak started and scored against third-tier Magdeburg and Bosz insists the 18-year-old striker is in his thoughts in the event of Aubameyang missing out.
"We have several attacking players who are threats in front of goal," he said.
"Alexander Isak is one of many options that could replace Aubameyang if he misses the match.
"Alexander is a very talented player. He showed that against Magdeburg."
Dortmund remain top of the Bundesliga but are only above Bayern Munich on goal difference after taking one point from their last two matches.
Germany's two footballing heavyweights clash early next month at Signal Iduna Park but Bosz insists RB Leipzig - a point further back in third - are also firmly involved in a three-way title tussle.
"Of course [they are playing for the championship]," he added. "They are in the top spots.
"We can see Leipzig playing every week and they've got a great team with depth. So yeah, they are playing for the absolute top spots."