Asensio went down in pain in the 64th minute of Tuesday’s International Champions Cup game against Arsenal and was stretchered off.
The 23-year-old was a second half substitute at a time when the 13-time European champions were down by two goals and he helped set up Gareth Bale’s first goal for Real Madrid before scoring the equalizer himself in the 59th minute.
Real Madrid went on to triumph in the ensuing penalty shoot-out but Asensio’s goalscoring involvement has come at a cost for Los Blancos.
Real manager Zinedine Zidane appeared distraught after the game and told reporters: "It's worrying, he's gone directly to the hospital for tests but it looks bad."
Anterior Cruciate Ligament injuries usually take between six to nine months to heal, putting Asensio’s participation in the forthcoming campaign as well as Spain’s possible involvement in EURO 2020 in huge doubt.
The club has released an official statement on their website, which reads: "After the tests performed on our player Marco Asensio by the Real Madrid Medical Services he has been diagnosed with a rupture of the anterior cruciate ligament and the external meniscus of his left knee.
"The player will be surgically operated on in the next few days."
It remains to be seen whether Asensio’s injury could scupper Real Madrid’s plans of offloading Gareth Bale and Dani Ceballos.
Asensio, who scored in the 4-1 win over Juventus in the 2017 Champions League final, appeared in 44 games in all competitions for Real Madrid last season, scoring six goals.
