Id give him an 8. For his style of fighting. A swarming aggressive fighter his D was pretty damn good. He tucked his chin very well and he was able to slip and roll with shots better than given credit for. Heavyweights like Ellis, Quarry and Ali had blazing handspeed and Joe was right in their faces and yes they hit him but they also missed a boatload of punches. It is also true that his offense helped his defense in a way. As Eddie Futch stated Frazier made his opponents rush their punches and they had to fight Joe off of them more than they were fighting him. He didnt give them the time and room many boxers need.