Buddy McGirt fought for a long time and beat many good fighters with a wrecked left shoulder; he nearly beat Whitaker in their first fight with just a right hand.
He was able to do that because he used his brains and his feet to control distance, even against a guy smart like Whitaker.
PAC is fast and, if you stand there and let him, throws a lot of punches. He lacks smarts and has weak feet.