Reus, 30, has been out since February with the injury and had been expected to return to the Dortmund side post-lockdown, but his rehabilitation has hit a snag, with German publication Bild claiming that he “can’t shoot with his right foot without discomfort.”
The German international picked up the injury against Werder Bremen but had previously told 100% Bundesliga at the beginning of May that he was 100 per cent on track to return this month.
However, Bild are now reporting that he could be out for the rest of the season.
Dortmund returned to Bundesliga action on Saturday with a 4-0 dismissal of Schalke at an empty Signal Iduna Park but remain four points adrift of Bayern, who beat Union Berlin on Sunday.
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WHY BORUSSIA DORTMUND MAY WANT BAYERN TO WIN THE BUNDESLIGA
Meanwhile, Dortmund would benefit from not winning the Bundesliga title this season, according to the latest Game of Opinions podcast.
It’s a wildly inflammatory suggestion but German football expert Florian Bogner and Eurosport UK’s Pete Sharland believe there is little appetite for them to triumph.
"I know some Borussia Dortmund fans and they’re like, 'To be honest, we don’t want to be champions this year'," said Bogner.
Why? Because can you imagine winning a title in an empty stadium? Can you imagine someone holding up the Meisterschale in front of an empty stadium? Can you imagine doing a championship parade with nobody allowed to freak out?
"They will take it [the title] if it’s there, of course. But the approach is ‘just get it over with’. I think everything is falling into place that Bayern Munich will win it again and nobody will care about it afterwards."
Erling Haaland scored the opener at an empty Signal Iduna Park in the derby win against Schalke, and he and fellow youngster Jadon Sancho have been consistently linked with moves away from the club, with Sharland stating that a league win could hasten their departure.
"If they win the league this year, I think it might accelerate some of their best players leaving," added Sharland.
"But if they don’t win the league, they’re probably going to keep everyone together for at least another year, maybe two years.
"If this team stays together for two or three years, they could win the Champions League. There’s that much potential."
Dortmund host Bayern on May 26.