New arrivals Joao Felix and Joao Cancelo struck their first goals for Barcelona in an impressive 5-0 rout of Real Betis on Saturday in La Liga.

Earlier Atletico Madrid were hammered 3-0 by Valencia at Mestalla with coach Diego Simeone labelling it the "weakest" performance during his time at the club.

Barcelona's five-star display was inspired by Felix, who netted the opener, with further goals from Robert Lewandowski, Ferran Torres and Raphinha and Cancelo.

The emphatic victory places the Catalans provisionally top of the table, a point clear of rivals Real Madrid who host Real Sociedad on Sunday.

Barcelona played with a vibrancy they lacked at times last season, even as they lifted La Liga, warming up for their Champions League opener on Tuesday against Royal Antwerp.

Xavi handed Felix and compatriot Cancelo their first starts for the club and they quickly impressed home fans and their coach.

"We're talking about two players there are absolutely no doubts about in terms of individual quality," Xavi told reporters.

"The two bring something different that improves the team. Individual quality is what makes the difference."

"I'm very happy to be starting again, the feelings are very good -- it's easy to play in this team," Felix told Movistar.

Felix, signed by Atletico Madrid for a club record fee of 126 million euros ($134 million) in 2019, failed to find consistent form in the capital and was loaned to Chelsea last season.

"I am happy, the change has done me good, me and my family, I am very happy here," he added.