His approach to comping behind the big band set a high standard for other players, often using techniques that run against conventional wisdom.
For example, guitarists tend to accumulate chord fingerings the way squirrels gather nuts: one can't have too many of them, even if you don't remember exactly where they all are all the time.
Freddie's style relied on the use of three-note chord forms, chords which carry the important harmony for the music -- without the filler of duplicated notes (which often creates a muddier sound).
His mastery of chords and rhythm playing was phenomenal -- check out this quote about Freddie's knowledge from Wes Montgomery (found on allaboutjazz.com's "Musician of the Day" page): “It would be alright, but I don't know that many chords. I'd be loaded if I knew that many. I'd probably go join a (big) band and play rhythm, man, because he's (Freddie) not just playing chords, he's playing a LOT of chords.”
A lot of what he did used common ii-V substitutions ... it ain't rocket science, but it will definitely propel the music!