Bayern Munich said they are considering legal action against the Canadian soccer federation following Alphonso Davies' serious knee injury in a match of little importance.

"We're demanding a full investigation into the events from Canada Soccer and expressly reserve the right to take legal action," Bayern chief executive Jan-Christian Dreesen told the Bild on Friday.

Davies tore a ligament and sustained other damage in his right knee during Canada's 2-1 win over the United States in the third-place decider for the Concacaf Nations League tournament on Sunday.

Davies returned to Munich where the full extent of the injury was determined on Wednesday. The left-back underwent surgery and "will be out for several months," Bayern said.

The club allege that Canadian officials did not provide appropriate care for the player.

"Sending a clearly injured player with a damaged knee on a 12-hour intercontinental flight without a thorough medical assessment is, in our view, grossly negligent and a clear breach of medical duty of care," Dreesen said.

He said Davies should not have been playing at all.

"The participation of Davies, who already had muscular problems before the game, in a match of no sporting significance is incomprehensible from our point our view," Dreesen said.

Bayern sporting director Christoph Freund agreed, saying the treatment of Davies after his injury was "incorrect."

Freund said Davies had complained of fatigue after Canada's prior game but still played.

"He is the captain, a young man who wanted to help his team but it was borderline," he said.

"The second issue is the injury after 12 minutes. Then Phonzy [Alphonso] flies back on a 12-hour flight and we all assume it is not a serious injury but then we have this," Freund said of the discovery he had an ACL (anterior cruciate ligament) tear in his right knee.

"That is sloppy. It is not professional and we need to talk and clear it up. We are the employers, we pay the players, so we will be looking into what happened."

Davies is out for the rest of the season and will miss Bayern's final games as they bid to wrap up the Bundesliga title and reach the Champions League final at their home stadium in Munich. Bayern face Inter Milan in the quarterfinals.

Bayern can claim some compensation for Davies' salary from FIFA's insurance policy covering national team players' injury risk, up to $7.5 million per case.

France defender Dayot Upamecano also returned from Nations League duty with a knee injury, denying coach Vincent Kompany another option in defense with South Korea's Kim Min-Jae already out injured.

Bayern, who host St Pauli in the league on Saturday, have gone two games without a Bundesliga victory and their lead over second-placed Bayer Leverkusen has been cut to six points.

Coach Vincent Kompany said his team had enough quality to fill the absences and there were would be no excuses.

"It is a pity first of all for Phonzy and Upamecano, who cannot be with us at this crucial period of the season," he said.

"This season we had to compensate for other absences. Hopefully it will bring the group tighter together ... The reaction is what's important. There are no excuses for me. Just to win the next game and keep improving."

Information from The Associated Press and Reuters was used in this report.