BARCELONA • Barcelona made an attempt in the summer to shore up their defence with the €35 million (S$54.5 million) signing of French defender Clement Lenglet from Sevilla, but his arrival has done little to address the glaring deficiencies in their backline.

And after losing 4-3 to Real Betis on Sunday - Ernesto Valverde's men let in four goals at the Nou Camp for the first time in over 15 years - Gerard Pique admitted they had to get back to basics to fix their porous rearguard.

Although Barca still top the LaLiga standings, one point clear of Atletico Madrid, Alaves and Sevilla, they have by far the worst defensive record of the top-seven teams in the Spanish league, conceding 18 goals in 12 league matches.

"We know we have a problem," the former Spain defender, who endured a torrid time alongside Lenglet, told reporters. "It's not an individual thing, it's a group problem, it's basic stuff."

The home side trailed 2-0 at half-time and even though Lionel Messi struck twice on his return from a fractured arm - having not featured since Oct 20 - Betis became the first side to beat them at their home ground since Alaves in September 2016.

But while Barcelona have dropped points in five of their 12 league games this season, Pique shrugged off fans' concern over their patchy form.

"It's something sporadic," he insisted. "Our fans can relax, we are top."

In contrast, Real Madrid have cut the gap between them in sixth spot and the leaders to just four points after a 4-2 win at Celta Vigo, leading to Real director Emilio Butragueno expressing his delight with Santiago Solari, who was confirmed yesterday as permanent coach .

The 42-year-old Argentinian has led Real to four wins out of four since being installed on a caretaker basis following Julen Lopetegui's abrupt sacking last month.

AGENCE FRANCE-PRESSE, REUTERS