Flamengo supporters took to social media to reveal their regret after Pablo Mari made his Arsenal debut in the 2-0 win over Portsmouth at Fratton Park.
The centre-back was handed his first start for Arsenal since joining on a loan deal from the Brazilian side in January, and helped the Gunners keep a clean sheet to reach the FA Cup quarter-finals.
Mari, who had already made two appearances for the Under-23 side to build his fitness, was paired alongside David Luiz at the heart of Arsenal's defence on Monday night, but repaid Mikel Arteta's faith with a composed display on the south coast.
Goals from Sokratis and Eddie Nketiah ultimately sealed the Gunners' place in the next round, but it was Mari's performance which had many supporters talking online.
Fans of Mari's parent club Flamengo took to Twitter to rue their club's decision to loan the former Manchester City defender to Arsenal.
The defender played a key role in the club's domestic title success in Brazil last season, and also helped them to win the Copa Libertadores.
One supporter wrote: 'He is that good. We are still crying here, but I am happy for him. He gave us a Libertadores and national league. He deserves it.'
Others sarcastically said: 'He is horrible. My advice is that you send him back to Rio,' and 'He's rubbish. Return him asap.'
Speaking after the match, Gunners boss Arteta praised Mari's display in his first start for the club.
"I think he looked comfortable," Arteta said, speaking to Arsenal.com after the game.
"He is very vocal and very comfortable on the ball, always commanding the back four and he looked like he’s played here for months. I think we have a good player."
Luiz, who captained Arsenal on the night, was also full of praise for his fellow centre-back partner.
"It’s great, these kind of things we have to learn," Luiz told the official club website.
"I think we did great tonight, everybody was 100 per cent focused and we didn’t concede.
"I’m so happy for Pablo, he’s a great guy, a great player and he had an amazing game so we are here to help each other and we are here, 25 players, ready to play, ready to play for Arsenal and ready to give the best job.
"When it’s like that it’s a pleasure to play football as I will say to the guys, especially to these young lads who are starting football.
"They are starting with a great opportunity at a big club and they are doing great, so it’s a pleasure to play with them."
