The Toronto Maple Leafs are hopeful that three key contributors will be available for Game 1 of the Stanley Cup playoffs against the Washington Capitals.

Goaltender Frederik Andersen returned to practice Tuesday morning, following a worrying collision over the weekend, and was optimistic about starting the opener. Two defencemen, Nikita Zaitsev and Roman Polak, didn't make it into the 45-minute session and are seemingly in question to play on Thursday (CBC, CBCSports.ca, 7 p.m. ET).

"They didn't practise today so we'll see if they practise [Wednesday]," head coach Mike Babcock said. "Obviously both guys are progressing. We're optimistic both guys will be ready but I can't guarantee anything."

The Leafs at full health were already going to be challenged to slow the NHL's top team. The absence of one or both defenders and their starting netminder would increase the difficulty of that task.

Andersen said he felt "pretty good" after the practice, though he was less than definitive about starting the opener.

"Yeah, I mean if everything goes well, yeah," said Andersen. "Definitely want to work has hard as I can and do all the right things to be ready."

Andersen said he was required to go through concussion protocol after taking a hit to the head for the second time in two weeks on Saturday evening against Pittsburgh. Babcock said he suffered no concussion symptoms from the latest collision with Penguins forward Tom Sestito, but Andersen declined to discuss it when asked Tuesday.

"Not going to talk about that in the playoffs," he said.

Andersen suffered a concussion at about this time last year while still playing with the Anaheim Ducks.

Zaitsev's absence concerning

His absence, even for a game, would significantly hurt Toronto's chances against Washington, which has Braden Holtby, the reigning Vezina trophy winner. Andersen posted a .918 save percentage in his first year with the Leafs, a far better option than backup Curtis McElhinney, who's played in exactly one NHL playoff game, a 34-minute relief appearance with Calgary in 2009.

Zaitsev's potential absence on defence is obviously concerning to Toronto.

He left Sunday's finale after being crunched into the boards by Blue Jackets captain Nick Foligno, appearing woozy after the hit. The team said he suffered an upper-body injury.

A free agent signing out of Russia last summer, the 25-year-old played a huge role as a rookie. He soaked up 22 minutes a night on the team's top pair, racked up 36 points and also lined up on both the penalty kill and power play.

He and partner Jake Gardiner are pegged to match up against Alex Ovechkin and the Capitals top line when the series gets going at Verizon Center.

Polak took a bump to his left side from Brandon Dubinsky shortly after Zaitsev's departure Sunday night, playing only one shift after an extended period in the team's dressing room. He played almost 20 minutes per-game down the stretch for the Leafs, a trusted source of experience and toughness for Babcock, especially on the penalty kill.

The absence of the two defenders at Tuesday's practice threw the defence combos into a blender: Gardiner was connected with former Capital Connor Carrick; Morgan Rielly was teamed with Alexey Marchenko; Matt Hunwick was paired alongside Martin Marincin.

Veteran forward Tyler Bozak also sat out the practice for maintenance, but is expected to be fine for Game 1.