Barcelona, without their talisman and captain, Lionel Messi, went down to a Kike Garcia goal early in the second half but substitute Ousmane Dembele claimed a point for the hosts. Martin Braithwaite had earlier on missed a penalty in the first half and had another goal chalked off for offside by VAR.
The result left the Catalans in sixth place, seven points behind leaders Atletico Madrid, who have played two games fewer than Barcelona.
"You have to be realistic and admit that it will be very complicated," Koeman said while assessing Barcelona’s title chances after they dropped points for the eighth time in 15 league games this season.
"In life nothing is impossible, but now there is a big difference in points with the leader, Atletico, who are doing very well, winning almost all their games and conceding very few goals. It's going to be very difficult."
"In the first half we had problems getting the ball from behind," he added. "We did not look for a game between the lines and I do not know why, but we have had opportunities again.
"I don't want to say that we lacked experienced players. There is a transition in the team, there are injuries and we play with many young people.
"But today there was a lot of experience in the team and, yes, we were missing Leo who makes a difference. But the feeling we have is that it was possible to have won because we have created enough chances."
