Brian Norman Jr. knocks Jin Sasaki OUT COLD with a left hook in the first minute of round five. It's an absolutely brutal finish as Sasaki is still lying flat on his back in the ring more than a minute later with members of his team and medical staff huddled around him. There are no celebrations from Norman.

Rising welterweight standout Brian Norman Jr. continued his ascension up the boxing ladder Thursday with a crushing one-punch knockout.

Brian Norman Jr retained his WBO welterweight world title by stopping Jin Sasaki with one explosive punch in Tokyo. The American dropped Sasaki twice in the first round and the one-way traffic continued once the challenger rose quickly to his feet.