The hosts came into this match having won just one of their previous five league matches, one of which was a defeat against UD Las Palmas at this ground last time out, but that poor run of form only looked likely to continue inside the opening five minutes.
With the first chance of the encounter, Oscar Rodriguez’s corner was powered past Inaki Pena by Sergio Gonzalez courtesy of a bullet header, leaving Hansi Flick’s men with work to do.
Barcelona were on top for the rest of the half, but a combination of disappointing end product and several last-minute blocks prevented them from launching a flurry of shots at Marko Dmitrovic. Their best opportunity came shortly after the half-hour mark when the Leganés shot-stopper tipped Raphinha’s first-time effort from inside the area onto the crossbar.
Lamine Yamal, who showed off his Golden Boy trophy to the supporters before kick-off, was uncharacteristically quiet, blazing high and wide seconds before the half-time whistle.
After the break, it felt very much like an attack versus defence as Barcelona dominated possession while their opponents looked to sit back on their slender lead. Still, the Blaugrana struggled to create opportunities, with Robert Lewandowski heading well over the crossbar 10 minutes after the restart.
Their best chance fell to Jules Kounde, but he could only sweep his low effort wide of the far post from close range.
All in all, Flick’s outfit did not do anywhere near enough to secure anything from this encounter in what was a lacklustre display. For Leganes, this victory – their first away from home of the campaign – could be crucial for their hopes of avoiding the drop as they move four points clear of the relegation zone.