Sevilla ended the game with 10 men after defender Jules Kounde was sent off in the 76th minute when he lost his cool and hit Javi Puado while trying to break free from the Espanyol winger's grip.
To add to Sevilla's woes, forward Anthony Martial had to be substituted early in the first half with a left leg injury.
"We were not ourselves against Espanyol," Sevilla midfielder Fernando told reporters.
"It was a complicated game, it was strange. We are struggling with injuries and inconsistency. The best thing right now is to not think about how far we are from the lead. We need to focus game by game."