San Francisco 49ers running back Jerick McKinnon reportedly suffered a "concerning injury" during a team workout on Saturday, according to NFL Network's Ian Rapoport and Mike Garafolo.
The 26-year-old previously gave the 49ers a scare when he suffered a knee injury late in training camp that required an MRI. Ultimately, the scans revealed a muscle strain, and he was given the all-clear to return to the field following some cautious maintenance work by the coaching and medical staffs.
Since then, San Francisco's $30 million man has been trying to work his way back to full strength in hopes of getting ready for a Week 1 tilt against the Minnesota Vikings.