The Spain international is relishing the Champions League tie with Barcelona and insists a hard-working performance will see them reach the semi-finals
The Rojiblancos sit top of La Liga, one point ahead of Barca, and are looking to progress into the semi-finals of Europe's most prestigious club competition, with the first leg to played at Camp Nou on Tuesday.
And Costa feels his team are in great condition as they prepare to meet Gerardo Martino's men, but has warned they must maintain their effort levels in order to triumph.
"I believe the team is at its best," he told Atletico's official website. "We are first in La Liga, we have the possiblity to achieve something big this year.
"We know a quarter-final against Barca is very difficult, but people are very excited about playing this match.
"Barcelona is a team that has demonstrated for many years that they are one of the best in the world, to beat them we have to be in top shape and play close together because they can easily create chances to score.
"We're where we are because of the team we are, because we all run. We give our best and I think in a match like this, we have to be a team, we have to stick together because by being a team our chances are great.
"Some players can make a difference in a team, we have Koke, Arda [Turan], Diego Ribas, who are very talented and can turn a game."