Javier Mascherano voiced his concern with Barcelona's stunning loss to Celta Vigo, whom he claimed outplayed the reigning La Liga champions.
Barca's 100 per cent start to the season came unstuck at Estadio de Balaidos on Wednesday as Celta triumphed 4-1.
Celta put the Catalans to the sword, with Iago Aspas' brace either side of the break inspiring the home side.
Barca target Nolito and John Guidetti also struck, while Neymar netted a consolation with 10 minutes remaining.
It was the third time Barca conceded four goals in a game this season, having been humbled 4-0 by Athletic Bilbao in the Supercopa de Espana and 5-4 against Sevilla in the UEFA Super Cup.
Speaking post-match, Mascherano said: "The opposition not only beat us, they also outplayed us, which is worrying.
"Their players beat us one-on-one and they are worthy winners.
"It always hurts when we lose. This is nothing new to us, we're seasoned veterans.
"The best thing to do is turn the page, focus on Saturday's game and putting in a good performance."
Barca welcome La Liga newcomers Las Palmas to Camp Nou on Saturday.
