With a triple-option team, I don't think you ever say "desperation" when one of their 3 planned options remains open.
Sure, their QB, Marshall, was in a bad spot, planted and falling backward, but his pitch man was still more or less in position. I think he was just going through his options, as an option QB always does.
Yes, he read the defense and decided to keep the ball, to run counter to the flow of Volunteers players. He'd been doing it successfully all night.
Here's a freeze frame of the very instant he made that decision:
See how hard Marshall is cutting at that very instant? That's him making the decision to keep.
Though it doesn't show in a still photo, what Marshall seems to have keyed on was the flow of the defenders from left to right in front of him. All their momentum was working to put them, esp. McDowell (unblocked) and Taylor (about to be blocked by the pulling guard, or so Marshall would believe) outside with the pitch man.
So Marshall decided to keep and turn back against their flow.
What he couldn't know then was (a) Taylor would have the quickness to step inside the pulling guard's block, putting himself in position to meet Marshall, and (b) Jumper would slide up and inside the block of the right tackle (which he is doing at the very instant of the photo), leaving himself free to flow quickly to the point of impact as well.
Just as a side note, already mentioned by someone earlier, look how far on the other side of the formation Abernathy is, at this point. He hustled to get to where he tackled the "receiver" (Jumper did too, both of them came from the back side of the formation to make their contributions).