There's several problems with taking that read, and all of them are a result of losing those two timeouts to an injury and cheapshot. If you throw to the middle of the field and don't score, you have got to piss away a down to stop the clock, and giving away downs in last second goal-to-go situations is not smart football. Secondly, by the time you complete the play and get to the line and make sure everybody is set before you clock it, you've just run the clock down to about 10 seconds and taken away yet another of your available downs, leaving you with only two plays to score. If you complete that pass in between the hashes and Spiller is tackled short of the first down (which is a distinct possibility if the ball is not absolutely perfect), then you've got to hustle to the line to clock it, thereby wasting another down and putting you in a position where you've only got about 10 seconds and you're now staring at 4th down and only have one play to score.
Throwing that ball in the middle of the field short of the goalline would have been a questionable decision; throwing that ball in the middle of the field short of the first down marker would have been downright foolish. I'm guessing that Chan told him to either get the ball to the sideline or get the ball to the endzone, but whatever you do don't throw it in front of the 1stdown marker.