Pere Milla scored a late winner as Atletico stumbled to defeat in Barcelona despite leading through Julian Alvarez’s brilliant goal.
Atletico have been busy in the transfer market, with notable arrivals including Alex Baena, David Hancko, Johnny Cardoso and Giacomo Raspadori, in a bid to challenge Barcelona and Real Madrid for the title.
Angel Correa, Rodrigo De Paul and Cesar Azpilicueta have all departed as part of the rebuild after Simeone’s team finished third, 12 points behind champions Barca last term.
Barcelona kicked off their title defence with a 3-0 win at Mallorca on Saturday, while Real Madrid host Osasuna on Tuesday.
Slovakia centre-back Hancko had the best chance of a cagey opening half-hour for Atletico but could only head straight at Espanyol goalkeeper Marko Dmitrovic.
The visitors forged ahead in spectacular fashion in the 37th minute, though, as Alvarez curled a free-kick into the top corner, well beyond the dive of Dmitrovic.
Alvarez went close to doubling Atletico’s lead just before the hour mark when he crashed a shot against the post.
Espanyol hit back 17 minutes from time as Miguel Rubio netted after a set-piece.
Substitute Milla completed the turnaround, heading in Omar El Hilali’s cross to snatch all three points for the home side in the 84th minute.
Athletic Bilbao got off to a winning start as substitute Robert Navarro’s late goal sealed a dramatic 3-2 victory over Sevilla.
Nico Williams’ penalty and Maroan Sannadi’s strike put the Basque club two goals up at half-time at the San Mames.
But Dodi Lukebakio fired in off the post on the hour to cut the deficit before Lucien Agoume drew Sevilla level with 18 minutes to play.
Navarro had the final say in the 81st minute, though, giving Bilbao an opening win as they look to back up a fine campaign last term when they finished fourth to qualify for the Champions League. (AFP)