Excuse me if this sounds too harsh.
If you have not noticed ( and judging by your above comments, you haven't ) Mariota was a running threat in college. To clarify my positon, Mariota rushed for ( 770 yards, 5.7 yards per carry and 15 TD's ) last season. Mariota ran a 4.52 in the forty yard dash. This is faster than Russel Wilson, or Colin Kaperniock! Mariota will be a good running threat in the NFL. Yes it is a factor.
But he's also a very good passer making him a dual threat. Last season Mariota ( 6'4" tall ) completed 68.3% of his passes, 4,454 yards, 42 touchdown passes, and just 4 interceptions. The season before MM only had 31 TD's and just 4 interceptions. This shows a QB who can pass for yards and take care of the football. Very important in the NFL. His character is also excellent.
By contrast last season Jamis Winston threw 25 touch downs and 18 interceptions, and fumbled the ball 7 times. This is the sign of a very mistake prone QB who averages well over a turn over a game. Winston also ran a slow 4.97 40, and has small hands which could be a reason why he's fumble prone. Yet the media pundits think he the #1 pick even though he has enough off the field baggage to fill a 767?
If Del is reading this, I think he would agree with me that Mariota's legs will be a factor in the NFL.