Because with a crippled foot he couldn't get in front of him. He should not have been in the game even as a decoy and definitely not to pass block. Just another dumb decision by the offensive staff.
There was no need for anybody to be a decoy. At that stage of the game only a Les Miles would even consider running the ball with a guy with a bad ankle. I would have either had Darrel Williams in to block or Guice if he is a good blocker or as a safety valve receiver