Lehtonen lost his helmet as he fell back into the goal after the hard hit.
"Obviously not good," Star coach Lindy Ruff said after Dallas' 4-3 win. "Likelihood, it's a concussion."
In Lehtonen's place, Tim Thomas made his Stars debut and stopped all six shots he faced. They acquired him from the Florida Panthers in a trade at Wednesday's deadline. Minnesota was leading 3-2 at the time.
Haula received 15 minutes in penalties, a major for charging plus a game misconduct.
It's really exciting. I'm pretty sure that when I play my first game I'm going to be emotional. To be back on the ice playing a game, being in game situations, with all the routines and rituals I do before games and during the game, I feel like I'm going to be emotional. I'm going to be really happy.
— Canadiens forward Tim Bozon on playing for the first time since his life-threatening illness