Casillas: Oblak decided the Madrid derby - not the referee
The Real Madrid captain was full of praise for the Atletico shot-stopper, feeling the Slovenian had a bigger bearing on the game than the under-fire Serbian match official
The visitors bossed the first half but could not make their superiority count, with home goalkeeper Jan Oblak pulling off a string of impressive saves, the best of which was a smart block to deny Gareth Bale.
The stalemate leaves the Champions League quarter-final tie finely poised ahead of next week's return at the Santiago Bernabeu.
Asked if he thought 0-0 was a good result, Ancelotti told ITV: "It's a result but not so good because we played really well in the first half. We are happy for the performance of course, the first half was really good. We have to try to repeat it in our stadium."
On Bale's early opportunity, he added: "[It was a] Good save, the goalkeeper was very important for Atletico in the first half. Gareth played a good game. I'm really satisfied, we worked hard all game, the first half with a lot of quality, the second was more difficult."
The match became niggly as it wore on, with Atletico striker Mario Mandzukic engaged in a running battle with Madrid centre-half Sergio Ramos and full-back Dani Carvajal.
Mandzukic claimed he was deliberately elbowed in the face by Ramos - an incident which left the Croatian requiring extensive treatment to a cut - but Ancelotti shied away from the accusation.
He said: "I think in a game like this, with this pressure, it can happen. It was unfortunate, the contact between Mandzukic and Ramos."
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