The Blaugrana midfielder believes further league slip-ups could cost his side the title in La Liga.
The Catalan side is currently in a three-way tie at the top of La Liga with Atletico Madrid and Real Madrid on 60 points, and still has to face both sides: Real at the Bernabeu in March and Atletico at Camp Nou on the final day.
Heading into the business end of the competition, Busquets believes any dropped points such as a defeat similar to the one suffered against Valencia at the start of February could prove fatal for the club's title aspirations.
“We will pay a high price for any draw or defeat in the league," he told reporters. “Real (Sociedad) have a great team and it’s always a tough place to play. For years we know that it is a difficult rival. We cannot fail if we want to rely on ourselves and know what is at stake.
"After the Valencia game, it was as if it was the end of the world and three weeks later it’s all perfect – that’s not the way it is. We’re not yet at our best and we weren’t so bad against Valencia."
Busquets featured in Barcelona’s 2-0 win at Manchester City in the first leg of their last-16 Champions League tie on Tuesday, and is wary of their opponent's threat in the second leg.
“City are an attacking team and you need these big games in the Champions League," he said. "They maybe have it easier in the Premier League as they like, but in Europe a lot depends on your opponents. In the second leg, City will attack even more - they are away from home and they have to score.”
On the return of Lionel Messi, Busquets said: “For us, Messi is the best. We know it might take a while for him to get to 100 percent, but he’s improving with every game. He will be the best player in the world as long as he wants. With Messi in the side, we have the chance to win every title."