Johnson's early exit from Friday's practice was related to the heat, Brooke Pryor of ESPN.com reports.
Coach Mike Tomlin added that two other players, TE Connor Heyward and DL DeMarvin Leal, missed part of Friday's practice because of the heat. This seemingly confirms reports suggesting Johnson's injury didn't look serious, so he should get back on the practice field soon enough to continue building chemistry with second-year QB Kenny Pickett.