Toughness is just the sexier term used to describe perseverance, the act of showing enough pride in your game, your team, and your teammates to push through difficult times and thrive.
Last year's team had very little of that despite dressing a premier face puncher. There was no pride in this team and it showed when young players were railed with no response, when one goal deficits turned quickly into three goal deficits, when players alligator armed their board work.
What we want to support is a team that perservers without wilting, and that shows that they will take enough pride in themselves to show up to the grind instead of avoiding it. You can accomplish a lot if everyone has a common spirit and pulls in the same direction even if they don't have the talent to compete with the best teams yet.
That will be the first sign that the rebuild is yielding positive results at the NHL level, even if they still suffer in the standings. You have to have that first.