Speaking after a 5-0 road loss in Toronto on Saturday night, head coach Travis Green said Pettersson suffered a slight sprain to his medial collateral ligament.
"It’s not too bad," Green said. "We’ll have our doctors re-evaluate him when he gets home. It’s probably as good of news as we could receive."
Green declined to provide specifics on a timeline, but acknowledged it’s the type of injury that usually requires 1-2 weeks of recovery time.
Pettersson was hurt in the second period of a 2-0 loss to the Canadiens when he got tied up with fellow rookie Jesperi Kotkaniemi.
Pettersson was originally scheduled to have an MRI on Friday, but the exam was pushed to Saturday. The 20-year-old Swede remained with the team for the finale of the six-game road trip at Scotiabank Arena.
"I’m hopeful he can play very soon," Green said earlier in the day. "The sooner the better.
"He looks good. He’s walking around pretty well."
Pettersson easily leads all NHL rookies with 42 points (22 goals, 20 assists) — 17 more than Ottawa Senators centre Colin White heading into the weekend.
The NHL’s rookie of the month in both October and December, Pettersson was named Vancouver’s all-star representative earlier this week.
"He’s smarter than everybody else, so he can stand still and create space," Toronto head coach Mike Babcock said Friday. "You can say lots of things about him — he doesn’t look like he’s that strong. He just has the puck the whole time.
"Everybody keeps backing off, so he has space and he can shoot it and he can pass it and he sees it. He looks like a real player to me."
Vancouver (20-21-4), which has been shut out in three of its last four games, went 3-3-0 on the road trip. The Maple Leafs improved to 27-12-2.
The Canucks managed to go 3-3-0 in the six games Pettersson missed earlier this season because of injury, but scored just nine goals in regulation during that span.
Vancouver will now have its first four-day break of the season, and plays just six more times — all at home — the rest of January.
"There’s no magic formula," Green said of generating offence minus Pettersson. "Our team is a bit of a blue-collar team, especially when you take Petey out of the lineup."