Subpar field conditions could have led to A.J. Green’s injury.

The star Bengals receiver will miss six-to-eight weeks after an MRI revealed he tore ligaments in his left ankle, according to ESPN. Green, who suffered the injury during Saturday’s practice at University of Dayton’s stadium, likely won’t be ready for Week 1 of the regular season.

Cincinnati was practicing in Dayton as part of the NFL’s celebration of its 100th anniversary, as Dayton hosted the first NFL game. ESPN’s Adam Schefter said the field conditions at the stadium were “subpar,” though he added that the team examined the field and cleared it for use.

Green was carted off on Saturday and punched the bench multiple times in frustration after getting injured. He later used crutches to get around.