Ajayi cracked a rib during the Dolphins' 22-17 loss to Tampa Bay Thursday -- yet another setback in a summer that hasn't gone according to plan.
Ajayi missed a good chunk of training camp with a hamstring injury, but finally broke through late Thursday. He carried the ball nine times for 66 yards and also caught two passes for 37 more out of the backfield.
Ajayi is projected to make the team on draft pedigree alone, but the latest development could allow the Dolphins to stash him on injured reserve for the season. If so, it could potentially re-open the door for Mike Gillislee, who also had a big game Thursday.