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.
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."
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.
"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.
