Record signing Ousmane Dembele made his debut but Lionel Messi again made the difference as Barcelona maintained their 100 percent start to the season and opened up an early four-point advantage over Real Madrid.

Visiting Espanyol never looked like claiming anything from this local derby, with Barca in full control throughout as they totally outclassed their cross-town rivals.

Messi netted twice before the break and later completed his hat-trick, allowing manager Ernesto Valverde to introduce Dembele when the game was already won, and the young French winger wasted no time in making his mark by providing a perfect assist for Luis Suarez to complete the scoring.

Barca were dominant from the opening whistle, probing patiently and leaving Espanyol to chase shadows in their attempts to maintain the deadlock.

The visitors were initially successful in that aim, with their disciplined defending preventing the hosts from creating any chances in the opening 20 minutes other than a free-kick from Suarez which Pau Lopez safely got behind.

But then the visitors were sliced open by Ivan Rakitic, with his clever reverse pass to Messi – who should have been flagged offside – creating the kind of chance the Argentine rarely misses as he duly swept home with his trusty left foot.

The same two players combined again almost immediately as Rakitic slalomed through the defence and played a sharp one-two with Messi before forcing a good low save from Lopez.

But Messi didn’t need long to strike again, turning home from close range after Jordi Alba reacted quickest to a loose ball in the box and delivered a well-placed low cross.

Espanyol nearly gave themselves hope when Pablo Piatti smashed a snapshot against the post, but that was a rare attacking foray and the second half started with Suarez – who was enduring a frustrating night – denied a close-range goal by Lopez’s smart save.

Piatti scooped a great chance wide after a mistake by Alba, but Barca were always threatening and went close through Messi and Suarez as the chances continued to flow.

Samuel Umtiti did well to block Leo Baptistao’s shot, but Messi extinguished any doubts by completing his hat-trick with a crisp low finish from the bright Gerard Deulofeu’s smart pass.

Gerard Pique made it four with a powerful header from Rakitic’s inswinging corner, and in the last minute Dembele rounded off a perfect night for Barca with a pinpoint assist for Suarez to convert.