Bruins goaltender Tuukka Rask yanked after two periods in Game 5 against Islanders

Bruins netminder Tuukka Rask, who recently acknowledged he was less than 100 percent, was pulled after two periods of Game 5 against the Islanders at TD Garden.

It was immediately unclear if it was for performance reasons — Rask allowed four goals on 16 shots — or injury concerns.

Jeremy Swayman, his 22-year-old backup, started the third, and allowed a goal on his first shot as the Bruins fell behind by three goals in a game they eventually lost, 5-4.

Rask did not participate in Monday’s morning skate in Brighton, but that is not unusual for veterans. The 34-year-old moved slowly during warm-ups, his back appearing stiff.

Rask went the distance in all nine previous playoff games this season, ranking fourth among goalies in save percentage (.935) and third in goals against average (1.94).

In an appearance on WEEI before the second round began, Rask said his “game feels good, health is OK,” he said. “I’ve been playing, so that’s OK. I’m not as good as I want it to be, but obviously I’ve been playing and practicing. So I’m out there. That’s all that matters.”

Rask sustained what was believed to be a lower back strain March 7, and played just 20 minutes of action over the next five weeks. Before Game 3, coach Bruce Cassidy downplayed concern about his ace’s health.

“He’s fine,” Cassidy said at the time. “Tuukka’s been ready to go every playoff game. There’s no issue there. Someone asked me the other day — I think he just, like a lot of guys, there’s a few things here or there or he said something. He’s ready to go. He practiced in full today and he’ll be in the net tomorrow night.”

Cassidy also referred to Swayman, who has not started a playoff game, as a “very capable backup.” Swayman, a first-year pro, submitted a sparkling 10 games as Rask’s late-season backup. Swayman finished 7-3-0 with a 1.50 GAA and .945 save percentage, with two shutouts.

Matt Porter can be reached at matthew.porter@globe.com. Follow him on Twitter: @mattyports.