The play was a toss sweep to the right and every linebacker went that direction.....Steward over pursued and actually was jumping over a Georgia lineman to get even more out of position just as Gurley is turning back to his left while still in the backfield. What I thought was a thing of beauty was the block made by the Georgia center.....he was helping the RT push Jarrett (I think) to the right but once the DL was pushed out of position he released and turned back to his left to put a block on Reader. Reader was releasing from the LG block and was the only defender in position to make the play once Steward had moved so far to his left. All the center had to do was put a shoulder into Reader and that was enough to release Gurley through a huge hole.
In looking at the play in slo-mo it really seems like the whole thing broke down because of Steward being out of position. If Steward stayed in his gap he can make the play for little gain.....or alternatively if he had stayed in his gap the center would have chosen to put the block on Steward and Reader makes the play for no gain.