"This season is finished for him. We received the worst possible news, but it is what it is," stated City manager Pep Guardiola. "We are here to support him through his recovery, step by step, as we move forward."
Rodri suffered the injury to his right knee during the 2-2 draw against Arsenal on Sunday. Recovery from an ACL injury typically takes between six months to a year.
This setback could significantly impact City's pursuit of a record-extending fifth consecutive English Premier League title.
"We lack a player with his specific qualities, but collectively, the rest of the squad can compensate for what Rodri has contributed since joining us," Guardiola remarked. "We must work as a team and adapt to playing for several months without such a crucial player."
Rodri's significance to the team was highlighted last season when City lost four out of nine matches in his absence, compared to just one loss in 50 games when he was on the field.
He played a pivotal role in helping Spain secure the European Championship this summer and is considered a strong contender for the Ballon d'Or.
While he will be unavailable for the remainder of the season, Guardiola indicated that it may take even longer for Rodri to regain his optimal form.
"One must be cautious with ACL injuries; often, after nine months, players face muscular issues the following year. Therefore, the recovery process is extended. I believe Rodri will take more than just nine months to return to his best," Guardiola explained.
Rodri's injury occurred shortly after he expressed concerns that elite players might consider striking due to the increasing number of matches being scheduled as new competitions are introduced to an already congested football calendar.
The Champions League has undergone an expansion, resulting in two additional matches in the newly structured group stage. For the first time, next year's Club World Cup will feature 32 teams, a significant increase from the previous seven. This tournament is scheduled to take place during the offseason for many major leagues in June and July.
The restructured Club World Cup has led to a legal challenge from players' unions.
On Tuesday, Manchester United's manager Erik ten Hag expressed concerns that the heightened demands could make injuries to key players "almost unavoidable."
Manchester City is set to face Newcastle on Saturday, but will be without Kevin De Bruyne, who is still recovering from a strain sustained during the match against Inter Milan last week.