I have never actually heard anyone describe a long throw in
football as a haymaker.
A Haymaker is typically defined as a wild punch, thrown with all
of someone's might in the hopes of knocking out their opponent.
I would surmise that a color analyst would describe a long throw
as a haymaker if it has a debilitating negative effect on the
opponents defense. As in "the offense just knocked the defense down
with that haymaker". However haymaker is not a term that is
generally used in regards to football.