Of course there are definitions for it. That's just called denial. He's a mere footnote in history. I"m not trashing him, i actually like the guy, but no real results to show for a long career, so he's not in legend category.
Blake is no legend I agree, actualy funny to call him that. But he does have some very good results in his career which is in an elite category by any measure, top 5 ranked player at a point, Master Cup Finalist, Around 10 ATP 250 titles, Finalist of a few Master series, was a stone on Nadal shoe earlier on his career, won the Davis cup with the US and over the last 10 years he has been the second best American player behind Roddick. Anyway, no legend, but a protagonist American player for sure.