Stipe beats any version of Sergei except maybe that really early version of Sergei that wasn't in love with his hands and realized he knew some grappling.
Guys is incredibly lumbering and slow, he just has bricks for hands. Stipe is smart, and he'd fight like he is. That wouldn't require him to be a wrestler, either. He just would know to stick and move and not get cornered into a brawl. Despite the embarrassing Struve loss, has since proven his chin is good enough. He went the distance with JDS.