El Bilal Toure's first-half strike proved the difference as the Mali international latched onto a Luis Suarez ball looped into his path and cannoned a finish in off the crossbar at Power Horse Stadium on Monday (AEDT).

On the back of its Europa League exit to Manchester United, Xavi's side suffered a second successive defeat for the first time this season, missing the chance to go 10 points clear at the summit.

But opposite number Rubi will cherish a famous win for his side, as the upset helped to hoist it out of the relegation zone at the other end of the table.

Determined to ensure there would be no hangover from their midweek European loss, Barca looked to dominate possession from the first kick of the ball.

Yet it could not make its early chances stick and paid the price when Suarez brought down a long ball on the right flank, before lobbing a cross inside for Toure to finish via the woodwork in the 24th minute.

The visitor laboured in pursuit of an equaliser for the rest of the half and headed into the interval looking no closer to finding the answers.

With the need to muster a response pressing, Barca again sought to pile on the pressure after the break and restricted the host to defensive duties and a meagre share of the ball.

But, with Robert Lewandowski placing two headers off target in the final 15 minutes, the Blaugrana could not summon the magic moment to avoid a stunning defeat.