You have to be out of your mind to think that there is another welterweight out there that will push Spence the way that Porter did. Although shorter, Porter looked like the much bigger man. His back was extremely wide and muscular. He made Spence look frail. If you're from any hood USA, you've seen these types of freak athletes. Short, stocky and strong as a bull. Danny, Pacquiao and Thurman will not have the same success against Spence.
I think Crawford would beat Spence at the moment. Porter is strong and durable, but also has a bad habit of getting slopply as the fight progresses into the later rounds. I also think Porter needs to go back up to his natural weight class, since he’s looked drained his last couple of fights. Spence’s defense also still needs a lot of work, since Crawford has faster hands and is a more accurate puncher than Porter and would hit Spence with clean counters if Spence doesn’t get more disciplined about keeping his hands up.