Have you ever seen Vince Young run in person? I have, as I lived in Nashville when he was a Titan. Young is incredibly fast and explosive, which is why during his redshirt freshman season of 2003 he ran the ball 135 times for 998 yards, an average of 7.4 yards per carry. You should know all about Young, because the next year he ran for 192 yards against Michigan on 21 carries, that's 9.1 yards per carry! That year, he had 5 games over 100 yards rushing.
Comparatively, as a redshirt sophomore QB, Gardner ran 47 times for 101 net yards. That's 2.1 yard per carry. In the 5 games Gardner has started as QB, his highest rushing total is 52 yards, against Central Michigan. Against OSU last year, he rushed for -28 yards!
See a slight difference?
Gardner's a nice dual threat QB, but he's not Vince Young. He has nowhere near the speed and explosiveness.