Matthews was injured on a hit by Winnipeg Jets defenseman Jacob Trouba when he drove to the net during the second period of a 3-2 victory at Scotiabank Arena.
"I knew the guy was coming," Matthews said. "Trying to get a shot off, you don't really know what to expect because you're so close to the goalie, so you don't know if you're going to get hit going into the goalie. Obviously, he took the body, which is what you're supposed to do, and he caught me at the right angle."
Matthews leads the Maple Leafs with 10 goals and 16 points in 11 games after starting the season with seven-consecutive multipoint games. He was held without a point in each of his past four.
The Maple Leafs play the Calgary Flames at Scotiabank Arena on Monday (7 p.m. ET; NHLN, SN, TVAS, NHL.TV). They lead the Eastern Conference with 16 points (8-3-0) and will be going for their third consecutive victory. Coach Mike Babcock said there are no plans to recall a player from Toronto of the American Hockey League at this point.
If Matthews can return in four weeks, he would miss 12 games and face the Philadelphia Flyers on Nov. 24. The Maple Leafs went 11-7-2 when Matthews was out last season, including 5-3-2 when he was out with the right-shoulder injury.
Matthews said he will not play until the injury has healed fully.
"You've just got to let it heal, I guess, and do everything I can to stay in shape," Matthews said. "Obviously, it's not the position you want to be in, but at least you can still kind of skate once it starts to heal a little bit and feel better, get back on the ice, and try to stay in game shape.
"Regardless of the situation, your health comes first. It's early (in the season), so you want to come back when you're feeling ready to go and back to 100 percent."