Usyk would outbox him every round to a 120-108. Ruiz doesn't have the footwork nor the IQ to compete with Usyk.
Ruiz is too stationary. I think someone of Usyks size is the only real threat at the moment. He's proved that these huge guys are just target practice, he's always got a punching lane due to his agility and footwork and they can't keep up with his work rate. Another guy moving up from cruiser is probably his biggest test. He's beaten the low tier opponents, the gate keepers, belt holders, freakish fighters and one of the younger heavys and none have had an answer. If Ruiz was younger fitter and had foot work to speak of then he might be an interesting fight but not now.
Nobody thought Ruiz would beat Joshua neither. Nobody thought pac would bea.t DLH Too. Nobody thought Douglas would beat Tyson.