Toronto Maple Leafs forward Auston Matthews has been ruled out of Game 6 against the Boston Bruins, head coach Sheldon Keefe confirmed to reporters Thursday morning.

Matthews was ruled out of Game 5 with an illness that he’s been fighting through the vast majority of the series. Toronto staved off elimination after Matthew Knies scored the game-winner during the first overtime period.

It’s quite obviously a catastrophic loss for the Maple Leafs. Matthews scored 69 goals, the best output in 31 years and may be in line to win his second Hart Trophy in three years. He’s a one-of-one goal-scoring talent and he’s likely going to be nominated for the Selke Trophy this season, awarded to the NHL’s best defensive forward.

Keefe adjusted his top line in Game 5, where Max Domi centred Tyler Bertuzzi and Mitch Marner. The move paid dividends as Domi played his best game of the series and was a menace in the faceoff dot, while creating chances relentlessly for his linemates. It is widely expected that the Maple Leafs will run back the same lineup as they did in Game 5.

ESPN’s Emily Kaplan reported that Matthews suffered an injury while fighting through the illness.

“Auston Matthews did in fact have an illness, he was playing through it. While he was playing through that illness, something happened in conjunction with that illness and that’s what’s keeping him out. I know that sounds really vague and opaque but we will find out all the details whenever the Leafs’ season is over. He did have an illness and that’s what they’re using as the line right now.”

Matthews recorded one goal and three points in four games through the series — all of these points came in a tour-de-force Game 2 performance when No. 34 put the Maple Leafs on his back and alongside Ilya Samsonov, carried the team to victory.