The two forwards are expected to make their Canadian team debuts at the Canadian Tire Centre.
McDavid, 17, hasn't played since suffering a broken right hand during an Ontario Hockey League game Nov. 11. McDavid admits he'll be trying to shake the rust.
"Just try and play as well as I can I mean that's the main thing," he said. "I can't ask for too much, I've been off for a while.
"Just do what I can."
McDavid, expected to be one of the top two selections in the 2015 NHL entry draft, had 16 goals and 51 points in 18 games with the Erie Otters before the injury.
"I think it's a matter for him to get back into his rhythm," Canadian team coach Benoit Groulx said. "I thought he did pretty well last week in St. Catharines.
"It's only the feel for the game and the way he's got to go . . . I think he's just got to take one period at a time and keep things simple."
There's a chance fans in Ottawa could see McDavid on a line with Lazar.
"Obviously that'd be pretty special to play with a guy like that," said McDavid, who had a goal and four points in seven games at last year's world junior tournament. "He has so much experience and playing in the NHL he obviously has some good advice and plays a very pro-mentality type game."
Lazar, a Senators prospect, was loaned to Hockey Canada on Thursday after appearing 27 games for Ottawa. He had a goal and six assists while averaging nearly 13 minutes of ice time.
Ottawa had until midnight ET on Friday to decide whether to send Lazar to the tournament. The 19-year-old said it was tough awaiting the Senators' decision.
"It's been a roller coaster of emotions lately," he said. "I lost a little bit of sleep over it trying to figure it out, but the bottom line is it's an opportunity to represent your country and that doesn't come too often.
"(Excitement) was building up there with decision time. I didn't know what was going to happen. It was a unique situation to be in because both are good solutions."
Canada finished fourth last year, losing to Russia in the bronze medal game. That is serving as motivation for Lazar, a native of Vernon, B.C.
"To be here, the gold medal is one thing to check off from my junior resume," he said. "I'm still sour from the result last year and how our team played.
"I'm really going to try and take it upon myself to change that result."
Lazar and Buffalo Sabres prospect Sam Reinhart are front-runners to be team captain, a decision Groulx expects to make following Sunday's game.
"(Lazar) is giving us options obviously. Can play centre, wing, power play (and) penalty kill," said Groulx. "He's a competitor. He brings leadership on and off the ice so I think it's a big asset for us."
Lazar, who had three goals and seven points in seven games at last year's junior tournament, is already embracing a leadership role on the team.
"I've been to a Memorial Cup, I've played in this tournament last year and I have a little bit of NHL experience too," he said. "I can bring that pro mentality and just what it takes to, on a day-to-day basis, be in the NHL.
"I think it can really translate here."
Having spent the first two-and-a-half months of the season in the NHL, Lazar said his Canadian junior teammates have been picking his brain about the pro life.
"I'm trying to tell them what it's all about because it's pretty cool," said Lazar. "I know for myself, every game is a different story.
"I've line-matched against (Sidney) Crosby, the Sedins and that's been a real eye opener for me to see the skill… the best in the world play and I'm trying to share that knowledge."
Canada concludes its pre-tournament schedule Tuesday night in Montreal against Switzerland. The Canadians open the world junior tournament Friday night facing Slovakia at the Bell Centre.