The Argentine opened the scoring for the defending Spanish champions at the Santiago Bernabeu on 11 minutes, before Cristiano Ronaldo wrapped up the points with a second-half penalty.
"We won an important match and we hope to chain results together to allow us to remain in the championship," he is quoted as saying by Madrid's official website.
"I am happy because of the goal, the other day I scored [for Argentina against Chile] and it did me a lot of good.
"Today I could do it again in a game made difficult because of the injuries we have. I suffered a heavy challenge on Wednesday, but luckily I recovered."
Madrid remain eight points behind league leaders Barcelona.