The La Liga side were held to a 2-2 draw in the first leg at the weekend, but Aguirre has claimed that he was "happy with the performance".
"I'm happy with the performance of the players and we will follow the same line in the second leg," Aguirre told reporters at a press conference.
"The game was characterised by the chances to score and by the ambition of the two teams to win the game. But the two goals we conceded were avoidable.
"I'm happy with the performance of the players and we will continue on the same line in the second leg against Real Jaen."
Espanyol currently sit 10th in La Liga.