Ancelotti said: "It's a very big step towards winning LaLiga. We've got a big advantage, but we can't lower our guard. We need to pick up a few more points and these games will help us prepare for the Champions League semi-finals.
"Vinicius didn't like coming off and wanted to keep going. The forwards have put in a huge effort, especially after the last game. We always ask the forwards to defend and work for the team. They're the fastest, they try to attack deep and they use a lot of energy. I understand that he wanted to continue, but we had to bring fresh legs on.
"Bellingham arrived at the right time. He put in a lot of hard work, a lot of effort and he hadn't scored for a long time. He scored a goal today that could be crucial for the league.
"I don't want to give my opinion on what Xavi thinks because everybody has their own opinion. It was an even, competitive and hard-fought game. Barcelona had some good spells, just like us. We managed to win this game with the last bit of energy and that puts us in a good position in the table.
"As always, there are some situations. The goal wasn't given because there was no clear image to determine that the ball had gone in. The penalty for the foul on Lucas Vzquez seemed clear to me. I'll concentrate on our performance because it was good as was Barcelona's. They showed a lot of quality with their youngsters and the game was of a high standard."
Lucas Vzquez's performance, he added: "He's a very important player, not only for what he did today, but throughout the season. He's playing at a very high level, he competes with Carvajal, who is one of the best full-backs in the world. He's made a difference in other games as well. Carvajal could play today, but other players are doing very well this season, like Lucas and Modri. They are helping us very much in situations like this after the heavy workload of Wednesday's game."