He isn't really glass jawed, Katsidis stopped him starting with a big left hook (the same one that floored marquez and in the same round) but still didn't put him down, he also had that war with Johanneson then John Murrray before stopping them, and took massive shots from Ghislain Maduma before wearing him down. In fact the only time he's ever been down has been against Ricky Burns
When Mitchell fights like that, with his technical skills he's hard to beat. He looked very very impressive, and has clearly matured as a fighter. The lightweight division is very open, other than Crawford - there's a very real argument that he could beat all the other names in the division if he fights in that style and with the same concentration and focus.