Just days after Barcelona announced Lionel Messi would be leaving the club, new signing Sergio Aguero has been ruled out of action for at least 10 weeks.

Aguero sustained a right calf injury in Sunday's training session, before Messi gave a farewell speech at the Camp Nou after Barca were unable to sign him to a new contract. Messi is expected to join Paris Saint-Germain as a free agent.

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Aguero, 33, was unable to make his debut in the 3-0 victory over Juventus at the Joan Gamper trophy.

The ex-Manchester City forward underwent a scan on Monday morning and Barca announced Aguero will be out for up to 10 weeks, though club sources have told ESPN they are hopeful he will be back in eight weeks.

Barca coach Ronald Koeman described Aguero's injury on Sunday as a "setback."

"It's a pity he got injured and could not play 30 minutes at the Gamper," Koeman said. "It's a setback as he was training and can bring a lot to the team with his qualify up front."

Barca, who begin LaLiga at home to Real Sociedad on Sunday, are still without forwards Ansu Fati and Ousmane Dembele and Aguero's injury could make Barca rethink their summer transfer market.

Martin Braithwaite, who started on Sunday, could be on his way out of the Camp Nou after the Danish striker failed to gain regular playing time last season but is now likely to remain.

Barcelona still have Antoine Griezmann, who was linked with former club Atletico Madrid this summer. The France international scored 20 goals and set up 12 more in 51 appearances last season.

Summer signing Memphis Depay has shone in preseason and the Netherlands international received a warm reception by the Barca fans during Sunday's team presentation.

Depay scored his team's opener against Juventus and assisted Braithwaite for Barca's second goal.

"We've signed players like Memphis that are very effective," Koeman said. "Of course, it's always important to have the best but if it can't be, we will not change our ideas or way of playing.

"There are other players that can occupy that position. We've seen a good Griezmann. We'll need to step up and improve because we won't have Leo's goals."