Thomas Tuchel fears Borussia Dortmund will struggle without Pierre-Emerick Aubameyang in the coming weeks.
The prolific attacker will headline the Gabon squad for the Africa Cup of Nations and will consequently miss the resumption of the Bundesliga, with Dortmund due to take on Werder Bremen on January 21.
Aubameyang is likely to miss the match against Mainz the following week as well and could even be unavailable for the fixture against RB Leipzig on February 4 if Gabon make it past the quarter-finals.
The 27-year-old has already netted 16 times in 15 outings this Bundesliga campaign and Tuchel has acknowledged his absence will hurt Dortmund.
"We cannot achieve our goals without Auba," the head coach told reporters.
"He improves everyone around him. Everybody who plays alongside him knows that he can make the difference from out of nowhere. "
Dortmund sit sixth in the Bundesliga table halfway through the season with 27 points from 16 games, 12 points behind leaders Bayern Munich.