São Paulo's star defender Alex Telles has been ruled out for the remainder of the season after suffering a knee ligament injury in training.
The Brazil international sustained the setback during training on Friday and underwent surgery to repair the damage.
Telles, who joined São Paulo from Manchester United in January, has made 12 appearances this season but was forced off against América de Montevideo in their Copa Libertadores match last week with what appeared to be a serious injury.
He was replaced by Matheus Fernandes and is expected to miss the rest of the campaign.
The news comes as a major blow to the club, which currently sit second in the Brazilian top flight table and are bidding to reach the quarter-finals of the Copa Libertadores.
Telles has been a key player for São Paulo this season, contributing four goals and three assists in all competitions.
His absence will leave a significant void in the team's defensive line, with coach Paulo Sousa already having to deal with the loss of key defenders such as Bruno Guimaraes and Gabriel Barbosa.
However, Sousa remains hopeful that his side can turn things around and secure a place in the knockout stages of the tournament.
"We have lost two key players in Bruno Guimaraes and Gabriel Barbosa," he said. "But we still have other options and we will try to make up for it."
Sousa also confirmed that Telles' replacement, Fernandes, would start in Sunday's match against Botafogo, but warned that the midfielder would need time to adapt to the new role.
"I am very happy with Fernandes' performance so far," Sousa added. "But he will need time to get used to the new role and I expect him to play well."
Despite the setback, São Paulo remain optimistic about their chances of making a comeback in the Copa Libertadores. The club is still in contention for a spot in the group stage and Sousa believes they can overcome any obstacles that come their way.
"We have a lot of talent and experience in our squad," he said. "We just need to stay focused and work hard to achieve our goal."