It's now been revealed that he tore his ACL and has been placed on Injured Reserve, ending his season.
Even though Cobbs was the third string running back, his loss is still significant. Cobbs made an impact in almost every phase of the game - particularly as a key contributor to the Wildcat and an all-around special teams ace. Those roles will not be easily filled.
Miami's decision to keep four RBs to start the season will now pay off, as Lex Hilliard moves up the depth chart. In Cobbs' absence, Ted Ginn should begin to see all of the kickoff return duties, which actually should be an upgrade.
I thought that Miami would use Cobbs' open roster spot to active Matt Roth from the NFI list once he's eligible after this week, but the team went ahead and signed RB Kory Sheets off of the 49ers' practice squad. I believe the rule about signing another team's practice squad players is that Miami must now keep Sheets on the 53-man roster for a minimum of three weeks.
Sheets (5'11, 208) was an undrafted free agent out of Purdue this past year. And if you remember, I actually pointed out that he would have been a better option to bring on board for training camp than Anthony Kimble due to his pretty good Speed Score of 104.2, 6th best in this past year's running back draft class.
Sheets is not a bruiser; he's a finesse back who excels as a receiving option. Here is one pre-draft analysis of him:
Sheets is an effective north/south ball handler who can create his own yardage. He has been productive as a running back and pass catcher, and Sheets offers a lot of potential at the next level as a third-down back/situational runner.