Two goals from Gonzalo Higuain, and one each from Cristiano Ronaldo, Sami Khedira, and Kaka gave Real victory after Barcelona had reduced the gap to seven points with a battling 3-1 victory over Sporting Gijon on Saturday.
Madrid were dominant throughout and their quick passing and counter-attacking play, together with world-class finishing, was too much for a disappointing Espanyol side.
Real coach Jose Mourinho, who has already been installed as favourite to replace the sacked Andre Villas-Boas at Chelsea, opted to skip the post-match news conference, sending out his assistant Aitor Karanka instead.
“Everyone can see that Higuain is a special player. When he is not happy you can see it and when he is you can tell as well. Kaka is another who you can see it in his face when he is enjoying his football,” he said.
Koffi Romaric for the vistors and Kaka for Madrid both tried their luck from long range in the opening periods but once the home team grabbed a 23rd-minute lead, the result was never in doubt.
A stray pass out of Espanyol’s defence from Raul Rodriguez was intercepted by Mesut Ozil whose quick thinking found Higuain with a first time pass who in turn laid the ball into Ronaldo’s path for a simple finish.
It was Ronaldo’s 30th league goal of the season and paved the way for the easy victory that was to come.
German international Khedira got the second when he made and finished a swift passing move on 38 minutes for his first league goal for Madrid, giving his side a two-goal cushion at the break.
Within 90 seconds of the restart, Higuain added the third, finishing first time after Kaka’s charging run down the left.
Another swift counter attack by Madrid gave Kaka his deserved goal for a fantastic performance on 67 minutes.
Ronaldo galloped away down the left to supply Higuain with a pass and enough time to turn and play Kaka into space on the right side of the area for the Brazilian to finish neatly into the left corner.
Twelve minutes later and the Brazilian was the provider again with good work down the left to supply Higuain for his second of the night and 15th league goal of the season.
Valencia beat Granada 1-0 away from home thanks to a Sofiane Feghouli goal that strengthened their hold on third position.
Algerian midfielder Feghouli finished of a successful week after scoring the winner on his international debut against Gambia on Wednesday.
Valencia remain six points clear of Athletic Bilbao who moved fourth after earlier beating local rivals Real Sociedad 2-0.
Markel Susaeta scored a goal in both halves for Athletic to move them level with Malaga on 37 points, two ahead of Levante who welcome Real Betis on Monday.
The Basque Country derby was closer than the result suggests and Real Sociedad had their chances to level in an end-to-end second-half, before Susaeta stepped up to convert a spectacular free-kick 10 minutes from the end.
The result will give Athletic confidence ahead of their trip to Old Trafford on Thursday to face Manchester United in the first leg of the last 16 of the Europa League where they will be backed by more than 4,000 travelling fans.
Bottom club Zaragoza came from behind to beat Villarreal 2-1 at home with goals in the last five minutes from Luis Garcia and Abraham Minero.
Hernan Martinuccio had given the away side the lead on 15 minutes that they held for 70 minutes but Zaragoza fought to the end to take a crucial victory.
The defeat leaves Villarreal only three points clear of the relegation zone and nine points ahead of Zaragoza.