The Nail KO5, but he needs to play it safe and let Stevenson press the action and be the counter puncher in this one.
Other then a cashout fight Stevenson will probably retire before facing another live opponent especially Gvozdyk who would destroy him
Stevenson is such a hard call, plus he is a goof so you want to hate him, lol, But that power is always the question. Gvod has the skills, style and hight to beat Stevenson, he just has to keep at bay for the first several rounds. It would be shocking if Stevenson takes this fight.