Koeman concerned by Barca errors
Ronald Koeman says Barcelona cannot afford to keep making the kind of errors that cost them in Saturday's 1-0 defeat to Atletico Madrid.
Atletico's winner came just before half-time when Yannick Carrasco took advantage of a rush of blood to the head from Barca keeper Marc-Andre Ter Stegen to shoot into an empty net.
That proved the decisive moment in a tight contest as Barca struggled to break down a characteristically well-organised Atleti defence, while they also lost defenders Gerard Pique and Sergi Roberto to injury.
The victory for Diego Simeone's side, their first in the league over the Catalans in a decade, strengthened the impression that they will be serious title contenders this season along with defending champions Real and Koeman's Barca.
The Dutchman took charge at Camp Nou in August, replacing Quique Setien, who was sacked after a humiliating 8-2 defeat to Bayern Munich in the Champions League.
While Atletico, unbeaten in 24 league games, went joint-top of the table, Barcelona are tenth having suffered back-to-back defeats to Getafe and Clasico rivals Real last month.
After the game, Koeman said: "We played well in the first half, but a team like Barcelona cannot concede a goal in the 47th minute as we have done.
"Afterwards we have had two very clear opportunities to tie the game but we know that Atletico defends very well. The goal was our fault, it is not good and it can't happen.
"We must improve in attack or defence. We know that we must work hard to get results."
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