I would consider trading him this off-season because his already-modest trade value isn't going to get higher. If he stays health he's on pace for an excellent and career-best season, given he's already at 2.1 WAR in 83 games and he only had 2.0 WAR in 107 last year (and 2.0 in 160 in 2019).
But if he's only a 2.0 WAR player or misses 60 games again in 2023 (when he still won't be that expensive) I'd say he's as close to being a non-tender candidate as he is an extension candidate (which would also have this off-season obviously, if he gets to one year left neither side will do it).
Edit: wait, Rhys only has one season left before free agency huh? Well, that simplifies things really. Still think you might trade him given all the other 1B/DH types on the roster but he won't be worth much. He's too good to non-tender. And an extension that both sides can live with is super unlikely.