The result came off the back of a 2-2 home draw with Girona and Ernesto Valverde's side will be desperate to get back to winning ways when they host Athletic Bilbao this weekend.
The Blaugrana have won their last eight league games at Camp Nou against the Bilbao outfit and bet365 offer them at 1/8 (1.12) to claim another three points.
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Valverde has no real injury concerns ahead of Saturday's game. Barca started their midweek defeat with both Luis Suarez and Jordi Alba on the bench and they should both come back into the starting eleven this weekend.
For the visitors, striker Aritz Aduriz remains a doubt and has not featured since picking up a muscle injury in the first game of the season.
Barca's defeat on Wednesday night will certainly have caused a few alarm bells to ring.
Most concerning of all for the champions was how they failed to lay siege to the Leganes goal in search of an equaliser despite having nearly 40 minutes to find a way back into the game.
They should however be able to have more joy in front of goal at home to an Athletic side that have conceded in every game they have played so far this season.
This year the Basques look more exciting yet less solid than they did last season, and if they are as open at the back this weekend as they were on Wednesday, they will be made to pay.
Tips and predictions
Barcelona have kept just two clean sheets in six games this season, with Leganes, Girona and Huesca all managing to score twice against the Catalans, although they have netted 17 times themselves.
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