Presumably, Thornton would try to instruct the team with his habits, which are not winning habits.
For example, Thornton always took a very "relax, don't get excited, keep things light" in his approach to the playoffs and big games. That wasn't a strategy that worked out. I don't want him passing that attitude on to the prospects.
Or, take his steadfast refusal to modify his game and add a shooting element to it; "I'm a passer", etc. I wouldn't want him telling Eklund to focus on his playmaking ability but would want someone who pushed Eklund to be a more well-rounded player.