I don't think it can be locked down. If you mean like his lineup can't be touched, but he's still playing each week.
In the end, some will end up playing him 2x, others only once. So the ppl who do so twice obv have an edge in scheduling, but it's just 1 game, and it's not like the team you'll play in his place isn't one you won't have a reasonable expectation of beating.
I just meant no one should be able to trade with him. He's obviously not coming back to the league he's already out of the playoffs. Just leave his team as is and it'll be as fair as possible. IMO.