off the top of my head i'd go with jose luis clerc,
25 career titles and had outstanding head to head records against 3 greats of his era...7-7 versus lendl...5-5 versus mcenroe...3-1 versus connors.
along with borg he's probably the only guy who doesnt possess a single losing record against any of those guys.
another guy i think underachieved was tommy haas, talentwise he should of broken through a few times but seems the guy was born to be injured.
25 career titles and had outstanding head to head records against 3 greats of his era...7-7 versus lendl...5-5 versus mcenroe...3-1 versus connors.
along with borg he's probably the only guy who doesnt possess a single losing record against any of those guys.
another guy i think underachieved was tommy haas, talentwise he should of broken through a few times but seems the guy was born to be injured.