Maybe it's time for everyone (coaches, management, fans) to admit that maybe he's not the type of player who can handled 25 mins. a night.
D-men who can do that and do it successfully know how to pace themselves. They play more patient, more efficient, pick their spots better. McAvoy's style has always been high energy, relies on his all-world athleticism.
Sometimes it's hard to reign in a thoroughbred who wants to run, but that's on the coaches to do their thing and well, coach.
This team has 3 capable right-shot D-men in their prime (McAvoy, Carlo, Peeke) that can defensively go up against any opponent. Next season if they run it back with those 3 (likely), they should try and dial back McAvoy's minutes, especially in the regular season, so that he has more in the playoffs. His mistakes in these playoffs are mental, which tells me it's likely heavy fatigue more than it is poor hockey sense/decision making. If Carlo and Peeke can handle a bit more 5 on 5 and PK, and Lohrei can handle some PP Unit 1 duty, maybe they can get more out of McAvoy where he's at his best 5 on 5.