Scalvini suffered the injury playing for Atalanta on Sunday in their 3-2 home loss to Fiorentina. It was their postponed final game of the campaign, which was played a week after the 2023-24 Serie A season concluded for the other clubs.
The 20-year-old was substituted in the 84th minute and, visibly in pain, left the pitch limping and supported by two members of the medical staff.
Scalvini hurt his knee himself while attempting a tackle and immediately fell to the ground.
He was taken to hospital where initial tests showed a rupture of the anterior cruciate ligament, Italian media reported. He will undergo further evaluation in the coming days.
Atalanta coach Gian Piero Gasperini confirmed during the post-match press conference that Scalvini was immediately taken for an MRI.
"Let's hope it's not the worst thing, clearly the cruciate ligament. The dynamics of the injury aren't the best," he added.
Neither the club nor the Italy national team has confirmed how long Scalvini is set to be sidelined.
Italian media reported that Juventus defender Federico Gatti is a likely replacement for Scalvini, who would have been the youngest player in Luciano Spalletti's squad.
Scalvini's injury comes after Inter Milan defender Francesco Acerbi pulled out of Italy's 30-man preliminary squad on Thursday with groin pain.
Italy kick off their Euro 2024 campaign on June 15th against Albania before they face Spain on June 20th and Croatia four days later.