Koeman always knew he faced something of a rebuilding job at the club this season, but admitted after the game his side were not up to speed.

"If I'm realistic, the title is very complicated," he said. "Nothing is impossible, but you have to recognise the distance.

"Atletico seem to me to be very good, very strong. They don't concede many goals."

Martin Braithwaite missed an early penalty as Barcelona passed up a string of opportunities in the match.

"We deserved to win," Koeman added. "We did what we had to do. They only shot on goal once. We created chances, but we didn't score the penalty and then made a mistake in defence.

"We did enough to win. This is happening many times."

Lionel Messi, the subject of increasing transfer speculation as his contract ticks down, was watching from the sidelines as he nurses an ankle injury, while the absence of other key players also told for a youthful Barca side.

"I don't want to say we lacked experience," Koeman added. "There is a transition in the team. There are also injuries. We play with young players – today we had five or six – but we also had experience.

"We lacked Leo, who makes a difference. But the feeling is still, how did we not win?

"We created many opportunities, missed a penalty, and gave away a goal."

Koeman granted Messi an extended break over Christmas to help rehabilitate his ankle, with the forward having just returned to Barcelona from Argentina.

With the forward soon able to talk to other clubs as he moves into the final months of his contract, Messi's future could come to dominate the conversation around Barcelona in the coming weeks.

"It cannot be said that Barca play better without Messi," Koeman said. "He is on another level. In general we played a good game, but individual mistakes have cost us points."