The Italian is delighted with the two goalkeepers and is happy to continue rotating them each game
Karim Benzema scored the only goal of the game, with the result seeing Casillas break his own record for the number of minutes clocked up since he last conceded a goal - a figure which now stands at 592.
The World Cup winner was overlooked by Jose Mourinho in the second half of last season and replaced by Lopez, but Ancelotti has opted to rotate the two goalkeepers this term, with Casillas featuring regularly in cup games.
Reports have suggested the 32-year-old could look to leave the Santiago Bernabeu at the end of the season in search of the No.1 jersey elsewhere, but the Italian coach insists he is equally first choice.
"I have to congratulate him because he is playing brilliantly at the moment. He deserves his record and he is really helping the team," he said.
"He made a fantastic save [to deny Córdoba]. In every game, he is playing well. At the moment, the two goalkeepers are playing alternate matches and so Iker is as much our first choice as Diego López."
Gareth Bale endured a frustrating evening in Barcelona - but still managed to force a fine save out of Espanyol keeper Kika with a dipping free-kick - and Ancelotti pointed to the Welshman's work ethic throughout.
"I thought he had a decent game. Maybe he wasn’t as sharp as he normally is but he worked tirelessly in defence and in attack. The whole team played exceptionally well for about an hour. As far as his position is concerned, he has no problem playing down the right, he has done many times."