I know Coach Rhemann knows Jeremy very well and knows he's a good person who'd never hurt or take advantage of Jean deliberately, but once Jeremy and Jean start dating and Rhemann becomes aware of it, I want him to take Jean aside.
I want him to check up on Jean, ask some clear-cut questions, make sure that Jean isn't once again in a situation where (he feels like) he can't say no. Because after all, Jeremy is his captain. There is a power imbalance between the two, both because Jeremy is older but also because of Jeremy's position as his captain and partner. And even though Jeremy is a good guy, Rhemann just needs to make sure that Jean is saying yes voluntarily. That Jean knows he's allowed to say no to this and he'll still be part of the team and his position as starting backliner won't be affected by it.
It's not because Rhemann doesn't trust Jeremy. It's because Jean deserves better than people just assuming it's what he wants. The other Ravens mostly also just assumed Jean wants it. And Rhemann couldn't live with himself if he didn't make sure Jean actually wants to be with Jeremy.