Vinícius Júnior is set to miss eight Real Madrid games including their derby clash with Atletico Madrid, sources have told ESPN, after suffering a thigh injury in Friday's 1-0 LaLiga win at Celta Vigo.

"Following tests carried out on Vini. Jr by the Real Madrid Medical Services, the player has been diagnosed with an injury to the right biceps femoris muscle," Madrid said in a statement on Monday. "His progress will be monitored."

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Sources told ESPN that Vinicius, 23, is likely to be out of action for six weeks with what is the first muscular injury of his senior career.

That would see the forward miss six LaLiga games against Getafe, Real Sociedad, Atletico, Las Palmas, Girona and Osasuna, as well as Madrid's first two Champions League group stage matches.

Vinicius would also miss Brazil's World Cup qualifiers against Bolívia and Peru in September.

The forward was substituted in the 18th minute in Vigo after feeling some discomfort when sprinting.

"He wanted to carry on. It wasn't very serious," coach Carlo Ancelotti said after the game. "Then he tried [to run] and it hurt and we took him off. I think he'll be back after the [international] break. It's a shame, he started well, he looked unstoppable."

Madrid went into the 2023-24 season with just three senior forwards in their first-team squad: Vinicius, Rodrygo and summer signing Joselu.

Ancelotti has responded by adopting a 4-4-2 formation rather than his habitual 4-3-3, with Vinicius and Rodrygo paired in attack.

The team's top scorer so far is another new arrival, Jude Bellingham, who has excelled in a No. 10 role, with four goals in three league games.

Ancelotti said on Friday that Madrid would not look to strengthen in the last few days of the transfer market, despite Vinicius' injury.

"The attack is covered," Ancelotti said. "The data speaks for itself. We've scored six goals. Without Karim [Benzema], without Vinicius, we have resources up front."