Ronald Koeman's "incredible" Barcelona claim as Memphis Depay punished by Radamel Falcao

Radamel Falcao scored the only goal of the game to hand Rayo Vallecano victory, with Ronald Koeman's side dropping down towards mid-table on Sergio Aguero's full debut

Things went from bad to worse for Barcelona on Wednesday, with Ronald Koeman's side falling to a 1-0 defeat away at newly-promoted Rayo Vallecano, and the manager claimed it was "incredible" that his side took nothing from the game.

The Catalan club might have hoped for more of a cutting edge on Sergio Aguero's full debut for the club, but instead they remain down in ninth place in La Liga as their away misery continues.

Barcelona haven't won a single game on the road since Lionel Messi left the club, and the result at Vallecas increased the pressure on Koeman after a challenging summer.

However, the manager maintained he was happy with his team's performance but frustrated by their failure to take their chances, saying "I am worried about our effectiveness, of course, but not about our game."

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Barcelona were their own worst enemies, conceding thanks to a Sergio Busquets mistake and missing a number of chances to beat Rayo goalkeeper Stole Dimitrievski.

The North Macedonia stopper kept out Memphis Depay's second-half penalty, while Depay's Barcelona team-mates squandered chances throughout.

The only goal of the game came from a familiar face, with former Atletico Madrid forward Radamel Falcao outshining his South American counterpart Aguero to send his team into the top six.

"I think we had chances - good chances - but we didn't finish them," Koeman said, saying he felt his team had shown a high level of performance in both this defeat and their loss to Real Madrid in the Clasico on Sunday.

"The team has shown today and against Madrid to be at a high level, but it is not enough. What counts is the result, and for me it is incredible that we lost," he added.

Busquets, meanwhile, took full responsibility for his part in Falcao's goal after losing the ball in midfield.

"I was sleeping, they picked my pocket and it was completely my mistake," the Spain international admitted.

The result leaves Barcelona down in ninth and facing a battle to even secure a top-four finish this season.

After the match, Koeman suggested his team's squad upheaval has put them at a disadvantage compared to their rivals.

"The team has lost balance in the squad, lost very effective players, which shows," he said.

"In recent years other clubs have strengthened every season and we haven't, which also shows."

Barcelona included two summer signings in attack, in the form of Depay and Aguero, but both players arrived on free transfers in a summer which saw Lionel Messi leave Camp Nou.

Koeman's side also lost Antoine Griezmann on loan, as well as selling the likes of Ilaix Moriba and Emerson Royal, and called on teenagers Nico Gonzalez, Yusuf Demir and Gavi against Rayo. Barcelona's next game comes at home to Alaves on Saturday, before an away match against Dynamo Kiev in the Champions League.