So basically, the football field is 100 by 53 1/3.
Since you are looking for the diagonal, use the Pythagorean Theorem.
a^2+b^2= c^2
c will represent the diagonal, or hypotenuse.
a^2 + b^2 = c^2
100^2 + 53 1/3^2 = c^2
10000 + 2844.4 = c^2
12844.4 = c^2
= c
c = 113.3 yards
The diagonal is less than 200 yards.