Center Sean Couturier, who appeared to suffer a knee injury when colliding with the Islanders’ Matt Barzal in the second period Tuesday, was not in the lineup when the Flyers faced another elimination game Thursday.

That wasn’t the surprising part.

This was: Left winger Oskar Lindblom, cancer survivor, played in his first game since Dec. 7. At the time, he was tied with Travis Konecny with a team-high 11 goals.

After a grueling battle with a rare bone cancer — he had his last chemotherapy treatment about two months ago — Lindblom was in the lineup and played on the third line with Derek Grant and Tyler Pitlick.

“The fact he’s going to play tonight is a miracle,” NBC broadcaster Keith Jones said before the opening faceoff, before Lindblom helped the Flyers outlast the Islanders in double overtime, 5-4, to force a Game 7 on Saturday night.

Afterward, coach Alain Vigneault said that because the game went deep into the second overtime, he used Lindblom “a little more than I anticipated. Great young man that wanted to help his team and he did. ... For him wanting to play just says so much about the young man.”

Lindblom played 17:30 and had three shot attempts, two hits and a blocked shot in the emotional win.

“The kid has so much courage,” captain Claude Giroux said. “He played unbelievable, too.”

“I don’t think there’s anything that can describe how proud we all are of him and how much he means to this organization and our team,” goalie Carter Hart said after a 49-save gem. “A really special moment for him to come out for his first shift and to see the support, not only from our team, but the Isles all standing up and cheering him on, especially after our goal against (them). A lot of respect to them for that.”

Lindblom, 24, said the decision to play was made earlier Thursday.

“It’s hard to step into a playoff game, especially one of these where you have to win,” he said. “Trying to grind it out, and luckily we came out with the win here.”

Lindblom was asked at what point did he believe playing again this year was possible.

“Good question,” he said. “I was just trying to think positive thoughts during the whole chemo. I knew I would play one day, but I didn’t know when. Today’s the day. I’m just lucky to be out there and be with these guys.”

Michael Raffl (goal, five hits, plus-3) also returned to the lineup, while top-line center Couturier and second-line left winger Joel Farabee were out. Farabee took a huge hit from Adam Pelech in Game 5 and was not available Thursday.

“Nobody can replace Coots,” Vigneault said in a Zoom call with reporters Thursday afternoon. “Coots is obviously one of the best two-way centers in the league. Plays the 200-foot game and is very dependable and trustworthy.”

Just as he did Tuesday, Scott Laughton moved to the top unit and replaced Couturier. Laughton, who had been on the third line, scored the overtime goal in Game 5 as the Flyers stayed alive with a 4-3 win, and he tallied a third-period goal on a breakaway Thursday to send the game into overtime.

Laughton gave them a lift in Game 5. Lindblom gave them inspiration in Game 6.

By playing, “obviously he gives our team a huge boost of energy,” Hart said. “One of the guys said it was like he never left. It was pretty special to see him out there with us. It’s hard to describe, but it’s pretty amazing what he’s gone through and how much he’s overcome and persevered.

“For him to be here with us,” Hart added, “we’re so thankful and so happy.”

NHL initiatives

The NHL announced a series of initiatives focused on the fight against racism and “the mandate to make our sport and our league more welcoming and inclusive.”

The league and players association committed to several initiatives, including mandatory inclusion and diversity training for all players during the 2020-21 training camp.

Several committees have been formed to develop solutions. Valerie Camillo president of business operations for the Flyers, was named to the league’s new Executive Inclusion Council.

“This is a very exciting announcement,” said Scott Tharp, president of the Ed Snider Youth Hockey Foundation, which has been partners with the Flyers and has been at the forefront of inclusivity since founded by Snider in 2005. “We look forward to helping the NHL in making hockey and the life lessons it engenders available to everyone.”

Power-play funk

The Flyers entered the night clicking at just 8.7% (4-for-46) in the postseason — 23rd out of 24 teams that have participated in the tournament — and 0-for-7 against the Islanders.

“That’s an area we’ve been spending a lot of time on with our group,” Vigneault said before the Flyers went 0 for 4 in Game 6, . “A lot of video work. Obviously, there’s less practice time [in the postseason], but we are able to touch on things like today in the morning skate. I believe we’ve got the personnel. We’ve gotten some better looks lately. If we keep getting those looks — just like five-on-five — I’m confident the puck will find the back of the net.”

Bizarre stat

James van Riemsdyk scored on a slapshot Thursday for only the fourth time in his career, including playoffs and the regular season, according to Flyers stats guru Brian Smith,

Breakaways

The Flyers played their first multiple-overtime game in 12 years. In 2008, Mike Knuble had the winning goal against Washington in the second OT. ... The Flyers (64) and Isles (73) combined for 137 hits in the game. The hits for the Flyers and against them are franchise playoff records since the stat began being tracked in 1997-98. ... Giroux won 61.5 percent of his 39 faceoffs. ... Barzal, the Islanders’ top-line center who was accidentally hit in the face by Giroux’s stick on a follow-throw Tuesday, was back in the lineup and had a goal. … Entering the game, Kevin Hayes had the Flyers’ best plus-minus rating (plus-6) in the postseason, and Nate Thompson had the team’s worst rating (minus-4). ... The Flyers are now 20-0-2 when Hayes scores a goal.