Barcelona were held to a 1-1 draw with Eibar.
The Catalans were held to a 1-1 draw despite creating many chances. Koeman has now admitted that their title chances are slipping away after dropping so many points in the early stages of the league.
“I’m realistic, winning the title is complicated,” Koeman said after the game.
“Nothing is impossible, but we have to recognise the distance.
“Atletico look very good to me. They’re very strong and they don’t concede many goals.”
With Messi and Gerard Pique not playing, the Catalans had to put out an young side, who missed chances galore and lacked a decisive edge.
“I don’t want to say that we lacked experienced players,” Koeman said.
“There’s a transition in the team and we have injuries too.
“We’re playing young players, but today we had five or six young players and players with experience too.
“We missed Leo, who makes a difference, but the feeling now is that we should have won.
“We had chances, missed a penalty and gave away the goal, which was their only shot on target.”
Barcelona will be eagerly waiting for the return of Lionel Messi for the next match.