MADRID (Reuters) - Real Madrid will need to play with intensity for 90 minutes and not just the first half if they are to beat Barcelona in Sunday's La Liga Clasico, according to Real coach Carlo Ancelotti.

He praised his side for their performance before the break in Sunday's 2-0 win at home to Levante but was concerned by the way his players relaxed in the second period.

A Gareth Bale double, his first goals in 10 matches, had put Real in control by half-time but Levante pushed hard in the second half and had chances to get back into the game.

It was not the dominant performance Real needed to silence their critics after three matches without a win but at least they will only be a point behind Barca when they run out at the Nou Camp.

"The whole team showed more desire and focus and they all understood what they had to do," Ancelotti said. "We did that in one part of the match and on Sunday we need to do that for the whole match."

Bale, in particular, looked like he had a point to prove against Levante after he was one of the players targeted with whistles by Real fans upset with the team's recent poor form.

Ancelotti said Bale's resurgence may have something to do with the return to action of midfielder Luka Modric, whom he played with at Tottenham Hotspur, after a four-month injury layoff.

"Bale looked more motivated and more hungry," Ancelotti said.

"The presence of Modric offers more depth for Bale to link up with his team-mates. They know each other well, they played together at Tottenham and there's no doubt that Bale is more comfortable with Modric on the pitch."