Barca go into the game on the back of a home defeat to Las Palmas.
But Costa told Marca: "I don't think they're on a bad run, they lost their last game, but all teams lose. We have to respect them as a great team, but the best respect we can have is wanting to beat them.
"They're having a great season, they're leaders and it's not a coincidence, but at home we feel like we have a good chance of winning. I don't watch much football, but the few games I've seen I've really enjoyed."
On Mallorca qualifying for Europe this season, he also said: "Yes, because you can see the quality we have. In football you don't live on illusions, but day by day and each one does their job.
"Both the club and we are doing well and by working hard we will be closer to being higher up. We have a good squad, a good coach and we work well together. We don't look at the standings or the 24 points, just the next game. We have the team for it."