You get a feeling of what's going to happen in that first frame, but if you know Walcott you wouldn't be sure if he was just trying to sucker you in to rip you with a sneak left hook, or something else. However, it sets it everything in motion.

Frame 1: Joe holds ground expecting Rocky to come forward.
Frame 2: Rocky closes the distance.
Frame 3: Joe's not telegraphing a left hook, but you can see he's already set to throw a right hand, and takes one of Rocky's punches, I can't tell if he's rolling with it or not, but he doesn't stop him.
Frame 4: Rocky's clearly open after he's thrown his left, and Walcott is ready to throw right hand counter.
Frame 5: He begins to throw his right, and Rocky doesn't have the time to stop it. Frame 6: Boom! That Hurt Rocky Big Time!

Here's a question for you, what's Walcott's left hand doing in the meantime?