Miami Dolphins running back Jay Ajayi has been diagnosed with a concussion and will miss several practices.
Ajayi, who ran for 1,272 yards last season, sat out Wednesday's workout after being hurt Monday.
Safety Reshad Jones practiced for the first time in training camp after being sidelined with a calf injury. He started camp on the active-non-football injury list.
Ajayi's injury will mean more snaps in practice for backups Kenyan Drake and Damien Williams.