Sporting Gijon halted Barca's record 16-match winning streak when they held the champions to a 1-1 draw last weekend and Pep Guardiola's side surrendered the lead to lose 2-1 at Arsenal.
Barca still have a five-point cushion over second-placed Real Madrid, who host promoted Levante on Saturday, but another failure against the battling Basques would set nerves jangling in the Catalan capital.
"We are in good shape and there is no need to ring the alarm bells," Brazil defender Daniel Alves told reporters after the defeat in London.
The last time Barca slipped up in two straight games was when they drew 1-1 at Rubin Kazan in the Champions League group stage on September 29 and four days later were held 1-1 at home by Real Mallorca in La Liga.
Apart from a rare error from Victor Valdes, who let Robin van Persie's equaliser through at his near post, the most worrying aspect of Barca's performance at The Emirates on Wednesday was their squandering of numerous chances.
"They were very effective in front of goal and we were not," midfielder Xavi said. "In European competition you end up paying the price for that."
A run of four straight wins lifted Bilbao to fifth and boosted their chances of claiming a place in European competition for next season, although they were beaten 1-0 at Mallorca last weekend.
MEDIA ATTENTION
Real survived the second-minute dismissal of goalkeeper and captain Iker Casillas to grind out a 1-0 win at Espanyol last Sunday and are waiting to pounce on any more stumbles from their arch rivals.
Jose Mourinho's side were held to a 0-0 draw at Levante in September but thrashed the Valencia-based club 8-0 at the Bernabeu in the first leg of their King's Cup tie in December.
The outspoken Mourinho at times attracts more media attention than his players and his Portuguese compatriot Pepe said that has allowed the squad to focus on football.
"Before he came we felt the pressure that surrounds Real Madrid more," defender Pepe said in an interview with Marca newspaper published on Thursday.
"He tells us that we only have to concentrate on playing football and he creates all the necessary conditions for us to improve," he added.
Valencia climbed above Villarreal into third with a 2-1 win at struggling Atletico Madrid last weekend and host Gijon on Saturday. Villarreal are looking to end their two-match losing streak at home to bottom side Malaga on Sunday.
