Mauricio Pochettino's side have lost all three of their games so far and have even thrown away leads in their last two outings against Real Zaragoza and Levante, but the former Barcelona man believes they just need to convert decent first-half displays into performances over 90 minutes.
He told AS: "The team is calmer than people think. It is true that we haven't taken a point yet which can seem worrying, but we believe in our chances.
"We have played two very good first halves. The game against Zaragoza there was a sending-off and a penalty and against Levante we went too deep and conceded three goals.
"The fans aren't in the dressing room, they don't know what we do or how we are working.
"They have all the right in the world to have their opinion and, if we lose, to criticise us. It is logical, if I wasn't inside the dressing room I would think the same, but we will give our maximum to reverse the situation."
And the hosts could be boosted by the presence of Joan Verdu, who had seemed set to miss the game with an ankle injury, but the playmaker trained on Friday and could now be included along with Simao, who is expected to make his first start since joining from Besiktas.
Athletic, meanwhile, will be close to full strength for the first time this season as Fernando Amorebieta and Jon Aurtenetxe have returned from injury whilst Fernando Llorente is also included in Marcelo Bielsa's squad for the first time this campaign, with the Spain international now looking set to see out the final year of his contract.
However, captain Andoni Iraola believes Espanyol will be motivated by their poor start and is wary of a reaction in a fixture that Athletic have not won for over 14 years.
He told Marca: "In the three games they have competed but have conceded goals in the last few minutes. I am sure that during these two weeks they will have had time to correct the errors and they will be at 100% from the start."