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 title with a fifth-round knockout of Japans Jin Sasaki in Tokyo. Following the defeat, Sasaki was hospitalized and revealed memory loss spanning six weeks.