BOSTON -- Toronto Maple Leafs forward William Nylander sat out Game 1 of his club's first-round playoff series against the Boston Bruins on Saturday due to an undisclosed injury.

Nylander, who has not skated with the team since Thursday, did not take the ice for warmups at TD Garden. Toronto coach Sheldon Keefe has not revealed any details about Nylander's ailment which reportedly flared up after the Maple Leafs' regular-season finale on Wednesday against the Tampa Bay Lightning.

Nylander is coming off a career-best 98-point campaign and is a staple among Toronto's top six forwards. He's also on the Maple Leafs' No. 1 power-play unit.

While Keefe did not confirm Nylander's status earlier in the day, his teammates appeared resigned to playing without him.

"(It's) tough for him, but hopefully he won't miss too much, and he'll be back," defenseman Timothy Liljegren said. "(It's) hard to replace Willy. But we've had guys step up when guys go down all year, so it will be no different this time."

Nylander was the only Maple Leaf to dress in all 82 regular-season games, and hasn't missed a contest in three years.

With Nylander unavailable, Calle Jarnkrok is expected to slide into his power-play spot and Nick Robertson will step onto Toronto's third line. The 22-year-old figures to be an odd-man out when the Maple Leafs are at full strength, but he's earned a chance after appearing in 56 regular-season games, finishing with 27 points. Keefe, on Saturday, deemed "significant" progress even from a bottom-six position for Robertson.

"He works for everything he has," Keefe said. "He doesn't need many scoring opportunities."

Robertson's only other NHL playoff experience happened when he debuted with the Maple Leafs in the postseason bubble in 2020. There were no fans in attendance then, when Robertson scored his first-ever goal. Robertson didn't expect the atmosphere to be quite so docile when Toronto and Boston kicked things off on Saturday and was thrilled to potentially be taking part in it.

"It's everything," he said. "It's one of the things you'd see when you're a kid and you want to play in these environments. To be with the Leafs and play Boston in the first game? Nothing better than that."