The champions, who had Dani Carvajal sent off as they crashed to defeat thanks to second-half goals from Luis Suarez, Lionel Messi and Aleix Vidal, are now 14 points behind Barca and face a huge challenge in keeping their title defence alive in 2018.
Valverde, however, does not think Saturday's result is a decisive blow to the hopes of all of Barca's nearest rivals.
"We're happy. We beat a great team on their pitch," he told BeIN SPORTS.
"We're still in the first half [of the season] and there's a long way to go. I don't want to say anything; there's still everything to decide."
The first half was a cagey affair, with both teams set up with four central midfielders, but Barca took control of the game early in the second half when Suarez broke the deadlock, before Messi's penalty doubled the lead after Carvajal was sent off for a deliberate handball.
Valverde admits his players were thrown off their natural way of playing in a difficult first 45 minutes, but was pleased with the way they improved.
"They planned a game to stop us from playing," he said. "We had to go long. If we did not save ourselves from the first line of pressure, we didn't have the ball.
3 - Barcelona have won three consecutive La Liga away games versus Real Madrid for the first time in their history. Triumph. pic.twitter.com/lTXNRhRtM7— OptaJose (@OptaJose) December 23, 2017
"After that, we controlled possession. Bit by bit, the chances and the goals came.
"In a match like that, when it's so physical, it's most difficult at the start. Then we played with more ease.
"I didn't think Madrid were of it. In fact, Madrid are never dead. They attacked and had more chances with 10 men, if anything."