I don't think Usyk would hurt Tua, David is just too tough. I also don't think Usyk would even try to, because it is extremely obvious that his route to victory is to pitty pat his way through 12 rounds and he's very likely to do just that. Hate to say it but it would be a boring-ish fight. Tua's best chance would be to rile up Usyk like Huck did and try and make him want to exchange. Then again I can't remember Tua being an A-hole, doesn't seem in character for him.