No market line is available here, so this rests on UFC Stats and Elo, which scores it nearly even (51/49 Spivac). The stylistic question is whose grappling means more: Spivac is the proven heavyweight grappler, 3.82 TD/15 at a strong 59% accuracy, with submission wins over Derrick Lewis and Tybura, while Petrino is a converted light heavyweight whose 79% takedown defense was built against 205ers and two soft heavyweight tests (Petersen, Lane, Asplund, none ranked). Opposition quality is the separator: Spivac just outpointed the durable Ante Delija and has been in with Gane, Almeida, and Cortes Acosta, while Petrino's three-fight heavyweight streak came against the bottom of the division and he was knocked out by Jacoby and choked by Anthony Smith the moment competition improved at 205. Petrino is eight years younger, quicker, and defensively tidier on the feet (2.71 SApM vs Spivac's 4.23), so he can win rounds at kickboxing range if Spivac can't get hold of him. But Spivac's clinch entries against the fence are heavyweight-specific weapons Petrino hasn't faced, and Petrino's guillotine loss to Smith shows scramble vulnerabilities against real grapplers. Expect Spivac to absorb some early leather, then win rounds two and three with takedowns and heavy top control. Low confidence, both men have been finished recently and heavyweight variance is unforgiving.

Spivac's size-adjusted heavyweight grappling, 3.82 takedowns per fight, and 59% takedown accuracy give him the clearest route to victory. Petrino owns strong 79% takedown defense and the superior striking differential, making him dangerous early, but sustained clinch pressure and chained trips should become harder to stop as the fight progresses. Spivac is favored to establish top control and secure a submission during a scramble or back-take.