Better nown for training Joe Louis, Blackburn was a quality fighter himself, he holds a newspaper win over Joe Gans and has 3 draws and a NC from 5 bouts with Langford. He also fought Greb and Jack O Brien and gave good showings but ultimately he wasn't quite on there level.
From what I've read, people have said he was good enough to win a world title if he hadn't killed someone and got himself done for man-slaughter as he was hitting his peak.