Robert Lewandowski struck twice for Barcelona, along with goals for Alejandro Balde and Jules Kounde, while Javi Puado and Joselu pulled two back late on for the hosts.
After Real Madrid beat Getafe on Saturday they overtook Atletico by two points. Diego Simeone's side are no longer mathematically in contention to win La Liga
Espanyol striker Joselu headed against the post before the hour mark, and then had a goal disallowed for offside.
Real Madrid came from behind to beat Espanyol 3-1 and cut Barcelona's lead to six points at the top of La Liga.
Barcelona visit Athletic Bilbao on Sunday as they bid to preserve or even extend their nine point lead on Real Madrid, who host Espanyol Saturday -- in their last league matches before the Clasico at Camp Nou on March 19
Barcelona stumbled in the Spanish title race with a 1-1 draw against rivals Espanyol in a bad-tempered Catalan derby on Saturday
Real Madrid secured a 35th La Liga title on Saturday with four games to spare after a 4-0 home win over Espanyol.
Real Madrid will win La Liga at the Santiago Bernabeu on Saturday if they avoid defeat against Espanyol as Carlo Ancelotti's side look to secure the Spanish title before facing Manchester City in the Champions League next week
Barcelona started and finished strongly on Sunday night but sagged in between and drew 2-2 at neighbours Espanyol to cling on to fourth place in La Liga.
Real Madrid slipped to a 2-1 defeat at Espanyol on Sunday as Carlo Ancelotti's side followed up a shock Champions League reverse with their first Liga defeat of the season.
La Liga: Thomas Lemar scored a late winner as Atletico Madrid edged past Espanyol on Sunday.
Barcelona and Espanyol were both reduced to 10 men in the second half before Luis Suarez netted the winner for the home side at the Camp Nou.
Real Madrid registered a narrow 1-0 win over bottom club Espanyol to open a two-point lead over Barcelona at the top of La Liga.
Mauricio Potchettino recalled how he and Jose Mourinho had forged a close relationship during their days as rivals in Spain's La Liga.
On Friday the Spanish government announced that over 4,800 people have died in the country as a result of coronavirus after 769 people died in the previous 24 hours, a record one-day figure for fatalities in Spain.
Karim Benzema scored one and set up another in Real Madrid's 2-0 win at the Santiago Bernabeu
Barcelona continued their march towards the La Liga title on Saturday with a 2-0 win over Espanyol.
Gareth Bale had been out since January 3 with a calf strain but made an instant impact off the bench for Real Madrid.