The Catalan club dropped points in just one of their opening 17 La Liga matches - a 2-2 draw against Real Madrid - to top the standings by nine points.
Yet despite their fantastic run, defender Javier Mascherano is not underestimating the threat of relegation-threatened Espanyol, who lie 18th but are unbeaten in four matches under new manager Javier Aguirre.
"The holidays have gone well. Now we have to pick up the habits and normal routines to prepare the match Espanyol, which will be a very difficult opponent," the Argentinian told the club's official website.
"Besides needing the points, they have improved a lot with the coaching change. (Aguirre) changed the dynamics and will want to make a great game because it's a derby."
Midfielder Andres Iniesta echoed his team-mate's sentiments and added Barca can not fall into the trap of believing they have already won the league.
"We would be mistaken if we thought that the league is won. The situation is very good, but I am convinced that if we start believing that we can't lose, then it will surely happen," he said in an interview with Catalunya Radio.
"Here you play and you have the ultimate to give it your best."
Barcelona have been boosted by the return to the training base of head coach Tito Vilanova less than two weeks after undergoing surgery on a tumour in his throat.
It remains unclear whether the 44-year-old, who temporarily stepped aside at the Nou Camp with assistant Jordi Roura assuming control of the first team, will be involved in preparing his players for Sunday.
Defender Adriano (hamstring) and midfielders Cesc Fabregas (hamstring) and Alex Song (knee) may return from their respective injuries.
Victor Valdes is a doubt with the heel injury that ruled him out of the 3-1 win at Real Valladolid last time out although the Barca goalkeeper is confident he will feature tomorrow.
Espanyol's number one shot-stopper Cristian Alvarez is a major doubt due to a hamstring strain, while defender Raul Rodriguez could miss out after suffering from gastroenteritis on Friday.
The Periquitos are overwhelming underdogs against Barca due to their respective positions in the league although defender Joan Capdevila sees reason for optimism.
"Barcelona are the leaders in the table and are away ahead of the rest. But, some day they will have to lose. They will not always win," Capdevila told Marca.
"We are very conscience of the team we face, they are having a great moment and they are a great team. But, eventually they will concede points and we will try to make them cede some points this Sunday."