Real Madrid coach Carlo Ancelotti lamented his side's missed chances in a 2-1 home defeat by Valencia on Saturday, but urged his players to regain some focus ahead of their Champions League quarter-final clash at Arsenal next week.

Valencia did leaders Barcelona a huge favour by shocking title-chasing Real in their first win away from home in LaLiga this season thanks to a brilliant performance by Georgia goalkeeper Giorgi Mamardashvili.

Barcelona moved four points ahead of Real Madrid atop La Liga after they were held to a 1-1 draw against Real Betis.

Ancelotti acknowledged that winning LaLiga had become a long shot but that it should not affect their Copa del Rey and Champions League campaigns.

"We have lost the opportunity to fight for the league with more forcefulness but the (Spanish Cup final) against Barcelona and the Arsenal clash will be different," Ancelotti told a press conference on Saturday.

"(Arsenal and Barcelona) will attack more and the game script will be much different. Sure, we will have to be better at the back and be effective up front, but can't lose focus.

"It's a fact that it is not that hard for our opponents to score against us at the moment. But that is no use moaning about it.

"This is not a deserved defeat (against Valencia). Could we have done better? Sure, but it's not a lack of attitude. We deserved to win and it was because of details. We have to move on and focus on Arsenal on Tuesday."

Ancelotti was unsure who he will name in goal at Arsenal as he was forced to start 19-year-old academy goalkeeper Fran Gonzalez against Valencia with Thibaut Courtois and Ukrainian replacement Andriy Lunin sidelined with injuries.

"Courtois practiced today and he felt good about it. Because it is still unclear if he will be good to go, we decided not to risk by playing Lunin today. Both will have a few more days to recover and we will see on Tuesday which options we have," Ancelotti said.