Once Stefan Struve found his groove, there was no stopping him.
But Struve settled in during the second round and punished his opponent. A series of big right hands knocked Miocic from the ranks of the unbeaten, referee Herb Dean stopped the onslaught at 3:50 of the round.
It was the fourth straight victory for Struve (25-5), all via stoppage, and his sixth in his past seven fights.
"That's part of the game plan," Struve said. "I saw that he was slowing down in the second round. I caught him with an uppercut. I always want to finish, I'm locked and loaded for the kill.
Miocic (9-1), a hard-hitting EMT from the Cleveland, showed little fear of the 7-foot Struve's reach advantage in the early going, wading in and landing early and often on route to winning the round.
But Struve found his footing in the second round and began unloading on the granite-chinned Miocic. The end came after Miocic slipped. Though he got back to his feet, Struve met him with a huge right uppercut to the jaw. That started a flurry of six straight rights. Seeing that Miocic was out on his feet, Dean stepped in and stopped the bout.
"I heard some things about my power in the past, but I think they might change their opinion right now," Struve said. "I'm working on some things, I'm working on using my reach better. Some moments were pretty good, some weren't that good. I think I've shown I got a hard chin."