Carlo Ancelotti lamented Real Madrid's defensive errors as they squandered a two-goal lead in a seven-goal Clasico thriller against Barcelona, who are on the brink of winning LaLiga.

The Blaugrana are one win away from their 28th Spanish crown after roaring back from 2-0 down to beat their arch-rivals 4-3 on Sunday.

Two early goals from Kylian Mbappe seemingly had Madrid in control, and the Frenchman would later become the third player to score a Clasico hat-trick in LaLiga this century, after Lionel Messi (twice) and Luis Suarez (once).

The last Madrid player to net a treble against Barcelona in league action, meanwhile, was Ivan Zamorano in 1995.

But four unanswered goals from Eric Garcia, Lamine Yamal and Raphinha – who netted twice – between the 19th and 45th minutes were enough to win it for Barca.

With David Alaba, Eder Militao, Dani Carvajal, Ferland Mendy and Antonio Rudiger all out injured, Madrid fielded a makeshift backline with Aurelien Tchouameni enduring a particularly tough game at centre-back.

Los Blancos struggled to contain the top-scoring team in Europe's big five leagues this season (Barca have 167 goals in all competitions), leaving Ancelotti demoralised.

"We made some glaring mistakes that cost us several goals," Ancelotti said.

"In high-level matches against top opponents, you need to be on top of your game. We played well in attack but it's clear we can improve a great deal on defence."

With Barca now seven points clear at the top of the table, they can secure the title as early as Wednesday if Madrid fail to win at Mallorca. 

Irrespective of Madrid's result, a Barca victory in their derby against Espanyol on Thursday would guarantee the Catalans the trophy.

"Everyone can make whatever assessment they want," Ancelotti said when asked about the likelihood of Madrid failing to win a major trophy this season.

"We have to finish the season well and try to win the three remaining games."