Kittle, who sat out the 49ers' first official practice of the week Wednesday, is dealing with a groin injury that's considered serious enough to potentially sideline him for Sunday's season opener in Chicago, Aaron Wilson of ProFootballNetwork.com reports.
According to Wilson, Kittle suffered the injury in question during an unofficial practice session Monday and was unable to take the field when the 49ers began Week 1 prep in earnest two days later. Head coach Kyle Shanahan suggested Wednesday that Kittle's status would be evaluated on a day-by-day basis leading up to the season opener, but the veteran tight end may need to practice in some capacity Thursday or Friday to have a realistic shot at playing Sunday. Tyler Kroft would be the next man up at tight end if the three-time Pro Bowler isn't able to play in Chicago.