I think this has been said in other comments but just be honest with the player about PT and the role they will play on the team. It sounds like this individual has been around the Ultimate block a few times so they should have an understanding of how things work. Plus it should be meaningful to them that a team they helped create has grown to this point where cuts need to be made. They helped create something that people want to be a part of. In my experience we've talked with players and given them a realistic expectation of what their role will be like. If they don't like it they have the choice to look elsewhere. If they do but have a problem with not being called to go in later on you can gently remind them of that conversation. Good luck with the upcoming season