His field vision was amongst the best of all the QBs we've had here — & his ability to go through progressions was pretty rare, imo. And his speed was often downplayed by critics. He was straight-up a dangerous runner even against tough competition. He didn't have break-away speed, but his acceleration was very good.
But he was a bit too stubborn & brave for his own good. As limited as his arm was, fans often time remember his arm-strength at its lowest point — when he was very hurt and definitely shouldn't have been on the field.