Brazil have confirmed that Arsenal defender Gabriel is out of the squad for their game against Tunisia on Tuesday due to an adductor injury.
The centre-back went off just before the hour-mark in Brazil's friendly against Senegal on Saturday.
"Arsenal player Gabriel Magalhães was re-evaluated this Sunday [16th] and underwent imaging tests that revealed a muscle injury in his right thigh," the Brazil federation said in a statement."
"Therefore, the player will not travel with the team to the match against Tunisia in Lille. No other player will be called up to replace him."
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The injury will come as a huge blow to Arsenal, whose title charge this season has been driven by Gabriel's performances at the back.
He has been the lynchpin of a defence that has conceded just five goals in 11 Premier League games. The centre-back also has three goal involvements, including a late winner away to Newcastle United in September.
The injury puts Gabriel's involvement in their north London derby against Tottenham Hotspur after the international break at risk.