I was sitting on the 40 yard line behind the SMU bench, Row 2, so I had a very good look at this as it happened. Evan Johnson was in man press coverage on the outside (SMU bench side) and the receiver ran a post. Evan locked him up really well until the QB scrambled to his left and Evan, apparently thinking the receiver was no longer a threat, basically stopped his coverage and started ball-watching and he ran/jogged underneath the receiver on the route. The receiver continued his post at full speed.
Had the QB been able to get velocity on the throw it would have been a TD. The receiver was 7-10 yards behind Evan and was wide open. Thankfully the pressure got to the QB in time. I hope the coaches notice this and take the opportunity to reinforce the need to play your assignment through the whistle.
This was close to a crushing last-play disaster.