Grosicki sustained the injury in the 69th minute of Poland's 4-0 win in Tbilisi, a result that kept Poland top of Group D.
And the 26-year-old is now set for a lengthy spell on the sidelines in what will come as a significant blow to a Rennes side who are enjoying a six-match unbeaten run in all competitions.
The former Sivasspor man joined Rennes in January and has made 10 appearances for Philippe Montanier's men this season.
Montanier's side visit Brittany rivals Guingamp on Saturday in a rematch of last term's Coupe de France final, which Rennes lost 2-0.
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