The Poland international, who was ruled out of his country’s World Cup qualifier against England on Wednesday, has sprained ligaments in his right knee.
Bayern Munich face Paris Saint Germain, in a rematch of the 2019/20 final, in the first leg of their quarter-final on Wednesday 7 April, playing the return leg a week later.
If the German side progress they will face either Manchester City or Borussia Dortmund in the first leg of the semi-final on 27 April, which Lewandowski would also be a major doubt for.
The 32-year-old suffered the injury while playing in Poland’s 3-0 win over Andorra on Sunday, with the striker substituted just after the hour mark, and underwent scans in Munich on Monday.
Lewandowski is also set to miss at least four Bundesliga fixtures, with Bayern Munich leading Red Bull Leipzig by four points with seven matches remaining this season.
He has scored 35 goals in just 25 Bundesliga appearances this campaign, and was on track to break Gerd Muller’s 40-goal record, which the Bayern Munich legend set in the 1971/72 season.
After winning the Bundesliga, DFB Pokal and Champions League with Bayern Munich last season, and finishing all three competitions as top goalscorer, Lewandowski was named the best men’s player for 2020 at the Best Fifa Football Awards in December.
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