Borussia Dortmund have yet to decide who will replace Michy Batshuayi after the striker sustained a season-ending left ankle injury on Sunday that has put his selection for Belgium's World Cup squad in jeopardy.
Batshuayi, on loan from Chelsea until the end of the season, was injured in the final minutes of Dortmund's 2-0 defeat at Schalke in the Ruhr derby. He scored nine goals in 14 games.
"We have a few options," Dortmund coach Peter Stoger said at a news conference ahead of Saturday's meeting with Bayer Leverkusen. "We could make a one-to-one replacement with Alexander Isak, for instance."
Isak, 18, not seen much of the pitch since joining from AIK Solna in January 2017, and although Stoger said Isak "has sensed an opening in attack," it appears more likely Dortmund will play without a traditional central attacker.
"We could play one of the pacey wingers there," Stoger said, opening the door for Marco Reus or Maximilian Philipp to move inside.
Going into the final four matches, and with Champions League qualification at stake, Dortmund will need to replace Batshuayi against Leverkusen, Werder Bremen and Hoffenheim, as well as against strugglers Mainz, who they host on the penultimate match day.
Leverkusen overtook Dortmund for third on Saturday, moving ahead on goal difference following a 4-1 victory against seventh-place Eintracht Frankfurt.
Mario Gotze could be ready to make an appearance in the starting formation, though fellow Germany international Andre Schurrle has not trained with the squad all week and is unlikely to feature against Leverkusen.
But Stoger said that while he was aware time was running out for Gotze to impress Germany head coach Joachim Low, his task is to get Dortmund to qualify for the Champions League.
"Incredibly a lot is at stake for the club," Stoger said. "If [Gotze is] there and can play to his best, then there will only be winners. Yet, for all the understanding I have for every player's individual goals, it's about reaching our goals as a club."