Luis Enrique accepted responsibility for Barcelona's surprise defeat against Deportivo Alaves at Camp Nou after admitting that his decision to rest Lionel Messi, Luis Suarez and Andres Iniesta had backfired.
The Spanish coach made seven changes to the side that beat Athletic Bilbao 1-0 on 28 August and his team was well off the pace as Alaves inflicted the first competitive defeat on Barcelona since April.
Deyverson opened the scoring for the visitors late in the first half, which was cancelled out by Jeremy Mathieu's header. Ibai Gomez struck the winning goal midway through the second half after a mistake from Javier Mascherano.
Enrique brought on Messi, Suarez and Iniesta in a bid to try and salvage the game but the visitors held on to register a famous win.
"We were fragile in defence and we will have to go over that," the Barcelona coach was quoted as saying in his post-match news conference by ESPN.
"It's an area where we've been strong in other years, but we also lacked fluidity and precision.
"The second goal, after another error by us, hit the group hard and did a lot of damage because it was a demonstration of our defensive fragility.
"It's good for us to evaluate things and to recognise how difficult it is to compete in this league."
'Easy to criticise with hindsight'
Enrique said he accepted the criticism coming his way after his decision to rest players backfired.
"It is what it is. I'm the most responsible for that and I accept [the criticism]," he stated.
"Everything bad that happens is my fault, but it's easy to criticise with hindsight.
"This season we don't just move forward with 11 players, we move forward with 22."
Barcelona are fourth on the La Liga table after three matches, three points behind leaders Real Madrid.
The Catalan giants' next assignment sees them hosting Scottish champions Celtic at Camp Nou in Group C of the Champions League on 14 September.