The center is expected to be sidelined at least three weeks. The Maple Leafs open the season at the Montreal Canadiens on Oct. 12, and that timeline could keep him out at least four games.
Tavares sustained the injury in a 4-1 preseason win against the Ottawa Senators on Saturday. He had one shot on goal in 17:14 of ice time. He practiced Monday on a line between left wing Denis Malgin and right wing William Nylander but did not practice Tuesday.
"He has been dealing with something since the game the other night," Toronto coach Sheldon Keefe said Tuesday. "He thought it was pretty minor, but they had some further tests here later today after we started practice and it has come back with an oblique strain that is going to keep him out a minimum of three weeks.
"He's a huge part of our team and it really does alter the plan for sure. But we've played without guys before, so for the remainder of the camp it just is additional opportunities for guys to step up and fill in that space."
Tavares was fourth on the Maple Leafs in goals (27) and points (76) in 79 games last season. He has scored at least 24 goals in 12 of his 13 NHL seasons.
"You are not going to replace John, but it does create extra opportunity for us to look at others and others to step up and take advantage of that opportunity," Keefe said. "At the same time, John and our medical team will do all they can to get him back as soon as possible."
Pontus Holmberg replaced Tavares with Malgin and Nylander at practice Tuesday but Keefe said he is not sure how the Maple Leafs will line up without their captain. Keefe said Alex Kerfoot, who was on a line with left wing Nicholas Robertson and right wing Nicolas Aube-Kubel in a 4-2 preseason loss to the Senators on Saturday, and Calle Jarnkrok also will be considered at center on the second line.
Auston Matthews, who led the NHL in goals last season with 60, is the first-line center.
"This is fresh information and I have not had a whole lot of time to process it, but we've been putting Alex at center] throughout camp, Jarnkrok has the ability to play up the middle, [and] I've been really happy with Holmberg's camp so far," Keefe said. "We've got a number of different options."
Tavares is the latest injury the Maple Leafs have dealt with during training camp. Defenseman Jake Muzzin did not practice Thursday and Friday because of back discomfort but skated Tuesday for the second straight day and is expected to join the main group as a limited participant Wednesday.
Defenseman Timothy Liljegren had surgery Sept. 16 for a hernia sustained during the offseason and is expected to be out six weeks.
Forward Pierre Engvall sustained a foot injury while training in Sweden during the offseason and will be reevaluated next week, general manager Kyle Dubas said Sept. 21. Engvall has been skating on his own since late last week.
Forward Adam Gaudette sustained a shoulder injury against the Senators on Saturday and is day to day, though he skated on his own Tuesday.
Defenseman
[Rasmus Sandin
, a restricted free agent, is not at training camp.
"It's no secret you need to have depth," Keefe said. "It comes at various times, your needs, we hope that this is the time where we need it and we can be healthy the rest of the way. The good news is at this point, the potential for guys to miss time like John, like Liljegren, like Engvall, like Muzzin, nothing seems to be too serious to the point where we would expect to be close to full health if not opening day, not far after that."
