TORONTO -- The Toronto Maple Leafs have lost one defenceman to injury and gained another.

Nikita Zaitsev will become the 10th Leaf to make his playoff debut this spring, ready to rejoin the team for Game 3 on Monday night after sitting out the opening two games of a first round series against Washington with a suspected concussion. Zaitsev will replace veteran Roman Polak, who suffered a season-ending injury in Toronto's 4-3 double-overtime win Saturday night.

"I feel better every day," Zaitsev said after the morning skate. "Now I feel good and I'm ready to play."

The 25-year-old will replace Polak on a pairing with Jake Gardiner, a duo that should match up against the Capitals' top line of Alex Ovechkin, Nicklas Backstrom and T.J. Oshie.

The other two pairs will remain intact from Game 2 with Morgan Rielly playing alongside Matt Hunwick and Martin Marincin lining up beside Connor Carrick.

Zaitsev hasn't practised since he was hammered into the boards by Blue Jackets captain Nick Foligno in the Leafs regular-season finale. He managed to skate the last couple of days and declared himself ready to play in Game 3 on Monday morning.

An NHL rookie this season, Zaitsev wasn't sure how he'd fare in his first playoff game -- especially off an injury.

"It's always hard to come back (because of the) speed of the games," Zaitsev said. "It doesn't matter -- playoffs or regular season. When you come back from injury it takes some time to feel good."

Toronto led the Leafs in minutes played during the regular season

"He's been a real good player for us all year," Leafs coach Mike Babcock said. "He's ultra competitive, moves the puck, good on the penalty kill, good on the power play, so an important guy for us."

Babcock was disappointed for Polak, who was injured in scary fashion over the weekend. He banged knees with Capitals defenceman Brooks Orpik late in the second period then landed awkwardly on his right leg. He howled in pain and had to be helped off the ice.

"It's bad luck," Leafs winger Leo Komarov said. "He's a warrior. He blocks a lot of shots. He plays easy. And he's tough. It's a tough loss."

Polak visited with the group ahead of Game 3.

"Obviously you never want to see somebody go down like that," Leafs centre Auston Matthews said. "Roman's a pretty important part of this team, not only on the ice, but off.

"He's obviously had a lot of experience, especially in these situations."

The Capitals could be without one of their top defenders, meanwhile, with Karl Alzner a game-time decision for Game 3. Alzner didn't skate on Monday morning and would be replaced by Nate Schmidt alongside John Carlson on the team's top pair.

Toronto will play its first playoff game on home-ice since May 2013.