“[It’s] tough for him, but hopefully he won’t miss too much and he’ll be back,” Toronto 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 Leafs player to dress in all 82 regular-season games, and he hadn’t missed a contest in three years.

He was missed on Saturday. Toronto amassed 36 shots on net but couldn’t solve Boston goaltender Jeremy Swayman in the opener. David Kampf, with the Maple Leafs already down 4-0 in the third period, accounted for Toronto’s only goal, with assists from Connor Dewar and Ryan Reaves.

Maple Leafs stars Auston Matthews and Mitch Marner combined for seven shots and nearly 41 minutes of ice time but couldn’t keep Toronto from a 1-0 series deficit.

With Nylander unavailable, Nicholas Robertson stepped into the lineup, entering Toronto’s third line. He finished with 14 shifts and 10:38 of ice time.

Game 2 is Monday in Boston.