This looks to me like a pretty evenly matched fight with the potential to be exciting. Both men have solid boxing skills and knockout power.
But Ruiz is the better boxer, and I think that's going to make the difference. He's a more accurate puncher with better footwork and timing. I think he'll be able to get the better angles on Hamer and land the harder scoring punches.
If Hamer can avoid Ruiz's big punches over the first half of the fight, things could start to change quickly. If the fight goes the distance, I think Hamer will eke out a close decision.
But ultimately I think Ruiz will land too heavy, too often in the early rounds. I'm picking him to win by Round 6 KO.
Ultimately, I'm not sure how relevant this fight truly is in the heavyweight division. Both men have talent, but last December against Vyacheslav Glazkov, Hamer appeared to still be on the wrong side of a steep learning curb.
Ruiz has the tools to be a true contender, but not so long as he's carrying so much extra weight.