It is a cruel blow for the Poland international, who had made an impressive start to life in France following his summer move to the Champions League club.
Nawrocki helped Lens defeat Paris Saint-Germain to win the Trophee des Champions, but he now looks set to miss the remainder of the campaign after suffering the serious knee injury.
Lens pledged their full support to the 25-year-old in a statement on Thursday.
They said on X: "Hang in there, Maik.
"Seriously injured, Maik Nawrocki is suffering from a complete tear of the anterior cruciate ligament and will undergo surgery.

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