Betis picked up just their third league win of the season courtesy of a double from Ruben Castro, and Lopez concedes that Espanyol's gameplan failed.
"We've lost against the team that's bottom of La Liga and we have to correct the mistakes we made. We set ourselves out to hold them in the first half and then go for the game in the second half," he told reporters at a press conference.
"If we'd done that, their fans would have started getting on their backs and their players would have started getting nervous. There's nothing we can do about it now though."
Espanyol lined up with three central defenders in Seville.