The Boston Celtics acquiredKristaps Porzingis, which obviously, makes them a better team on paper. But you don’t win NBA championships on paper, and it takes a lot to go the distance.

Porzingis is a great scorer, a solid rebounder, and a guy whose player profile was a seamless fit for Joe Mazzulla’s team. But in order to get him, they had to give away one of their leaders.

Recently, Marcus Smart pointed out the fact that GM Brad Stevens told him he was safe from any trades just before sending him to the Memphis Grizzlies. Obviosuly, that didn’t sit well with him.

Marcus Smart Regrets Never Winning A Ring In Boston

Even so, that’s not what bothers him the most about leaving the TD Garden. Instead, what keeps him up at night is that he wasn’t able to win a championship as a Celtic:

Not actually getting us one, that’s probably my only regret,” Smart said, per Boston Globe. “I love the journey that I’ve been a part of with this organization, with this team. I couldn’t ask for more. The only thing I regret is we didn’t get [the championship] when we had our chance when I was here. But other than that I’ve enjoyed my run.”

The Celtics even made it to the NBA Finals with Smart, but to no avail. And while there’s still a chance he comes back one day to finish the job, that could haunt him for the remainder of his career.