Miami Dolphins RB Jay Ajayi diagnosed with concussion, ruled out

The Miami Dolphins confirmed running back Jay Ajayi has been diagnosed with a concussion and ruled out of Wednesday's practice.

Ajayi, 24, was hit hard during Monday's full-contact practice and was escorted off the field. He will miss at least a week of drills, sources told the Miami Herald.

The 6-foot, 223-pound Ajayi led the Dolphins last season with 1,272 rushing yards and eight touchdowns in 15 games to earn his first Pro Bowl selection. He also caught 27 passes for 151 yards.

Backup running backs Kenyan Drake and Damien Williams will share first-team reps until Ajayi returns.

Dolphins starting safety Reshad Jones was activated off the non-football injury list and will practice for the first time since training camp opened a week ago. He tweaked his calf during personal workouts this summer.