i don't know about football, but i know that throwing a baseball is nothing like throwing the jav.
back in college i could throw a baseball at the same speed as our all-american javelin thrower (me being a 160 pound MD runner).
the jav was always a weak event at conference outside of the top 3 or so and 7-8th places were always especially bad. i figured i had a chance to score if i gave it a shot (a high jumper on our team had done that the year before after a week of practice). well, i tried to throw the thing in practice a few time and i dont think it went over 60ft. it would come out of my hand and then just turn over on its side almost immediately. maybe i was especially bad at the technique, but it just goes to show that being able to throw a ball 85mph doesn't mean you can automatically throw jav.