For me it has to be David Prutton.
I remember when it was first announced that he was coming to Saints.
I was genuinely shocked and excited about him coming, he had so much potential, was well thought of and could have been a real legend!
Sadly now only remembered for the punch up with the ref and the subsequent ban that possibly put a nail in our relegation coffin.
Still a pretty good player but never seemed to progress as he should. I guess football is littered with the same story.