LAS VEGAS -- William Nylander, who leads the Maple Leafs in scoring, went to the locker room late in the first period of Toronto's 6-5 overtime loss to the Vegas Golden Knights and didn't return because of a lower-body injury.
Teammate Oliver Ekman-Larsson also left the ice in the first but returned for the second period.
Maple Leafs coach Craig Berube said Nylander aggravated an injury that recently kept him out of the lineup for six games.
"He's back playing great and now he's out again," Berube said. "We'll see how long."
Nylander leads the team with 31 assists and 48 points after getting a goal and an assist against the Golden Knights.
His overtime goal gave the Maple Leafs a 4-3 victory at Colorado on Monday night to end the Avalanche's 17-game home winning streak.
The 11-year veteran has been an ironman for the Maple Leafs, having appeared in all 82 games each of the past three seasons and in 81 games in 2021-22.
The Associated Press contributed to this report.