If I understand correctly the player is offered a contract that signs him to the new team’s roster, but it does not have to be accepted. However he’d be giving up a significant raise to turn it down, and he has to on their roster (or at least paid like he is) for a minimum of three weeks. So it would be really unusual for it to be turned down. Not sure but it seems to me he or his agent could also go to his current team and give them the opportunity to match it, although that might get sticky if things went sideways.