TORONTO — Maple Leafs forward Auston Matthews has been ruled out for Game 6 of the first-round Stanley Cup playoff series against the Bruins on Thursday.

The Leafs trail the Bruins 3-2 in the best-of-seven series and face elimination with another loss.

Matthews missed the third period of Game 4 and all of Game 5 with what the Leafs have deemed a “lingering” illness.

Toronto’s top center has skated on his own the past three days — including for nearly 30 minutes prior to the Leafs’ morning skate Thursday — but coach Sheldon Keefe said it would be the team’s doctors ultimately making a call on whether Matthews made it into the lineup.

Toronto already extended its series once without Matthews available when they topped Boston 2-1 in overtime of Game 5. The Leafs planned to use a similar blueprint in Game 6 to grind the Bruins down and even the series one last time.

“It’s a bit of the human nature piece; you recognize everyone has to be better,” Keefe said of the Leafs performing well without Matthews. “It’s more the confidence our team has and how we’ve responded when players have been out. You’ve got to find a way to win a game … I think that piece is important. We have confidence there, we have trust in the group, and if anything, it just shows the strength of the group and not looking to others, but just doing your part.”

Max Domi moved into Matthews’ top-line center spot in Game 5 and was dominant in the faceoff dot (85.7%) while notching one assist. He also took over Matthews’ spot with Toronto’s top power play, which is a dismal 1-for-17 in the postseason. The Leafs also shuffled William Nylander — still adjusting to the postseason after being sidelined by injury for the first three games — to their second line.

Toronto did get a herculean effort from Matthews — who won his third Rocket Richard Trophy this season by pacing the league with 69 goals — prior to his illness absence through a three-point performance in the Leafs’ Game 2 victory.

Missing that type of difference-maker would be a hindrance for most teams, but the Leafs found ways to fill the Matthews void with a next-man-up mentality.

“Maybe instead of relying on him, we’re desperate to play good, because one of our best players is out of the lineup,” Nick Robertson said. “When you realize you don’t have a near 70-goal scorer in the lineup, we’ve got to find a way to play well.”

Toronto has no choice on that front. The Leafs enter Game 6 searching for their first playoff win on home ice in this series and have lost six consecutive postseason contests in their own building dating back to last year. They’ll have one final chance to change that and push the series to Boston for a decisive Game 7 — when Matthews may, or may not, be able to return.

“It’s difficult when one of the best players in the world isn’t available,” John Tavares said. “But it’s the nature of the game. Guys responded really well last game and it’s the same type of mentality. We’ve got to step up and do more and not have one guy trying to fill [Matthews] shoes.”