An injury-plagued Barcelona moved into first place with 14 points as Adriano gave them their first away win of the season yesterday.
Unfashionable Levante are tucked just behind on goal difference after a 1-0 win against Real Betis, while Real are a point further back in third spot ahead of Malaga and Valencia who also have 13 points.
After draws against Real Sociedad and Valencia, Barcelona went into their game at Sporting with a lengthy injury list.
Cesc Fabregas and Andres Iniesta were among the midfielders in the treatment room while neither Carlos Puyol nor Gerard Pique started in defence.
Adriano grabbed the only goal after 11 minutes, knocking in a rebound after a Xavi Hernandez shot came back off a post.
Eric Abidal went off injured after the break to add to Barca''s defensive worries but they never looked likely to concede.
"We played a strong Sporting who were very deep and worked together well. There was no space because they closed it down," said Barcelona coach Pep Guardiola.
"Always when we play after a Champions League game it is difficult but I think we did well in the first half and then faded after that."
Real Madrid have had a stuttering start to the season but have now bounced back from one point in two games with back-to-back wins.
Cristiano Ronaldo hit the post after just three minutes at Espanyol but Real went ahead after 17 minutes with Ronaldo setting up Higuain.
Kaka should have added to their lead before keeper Iker Casillas also blocked shots from Thievy Bifouma and Sergio Garcia for Espanyol.Midway through the second half Higuain hit a powerful drive into the top corner while Vladimir Weiss missed a good opportunity to reduce the deficit.
Substitute Jose Callejon slotted in a third against his former club and Higuain completed his hat-trick a minute from time as Real condemned Espanyol to their first defeat at home.
"I was happy with the way all of my players performed and also that of the opposition," said Real coach Jose Mourinho, who has complained in recent weeks that rivals have sought simply to defend against his team.
"The 4-0 scoreline was a result of our first two goals as they then had to attack and this extra space allowed us to score more. We are now only a point off the lead which is not a big problem."
Levante had Juanlu Gomez to thank for their 1-0 win over former leaders Real Betis, their fourth successive victory.Promoted Betis won their first four games on the trot, but yesterday succumbed to their second straight defeat.
Arouna Kone had a couple of excellent chances to score either side of Juanlu's volley from a Valdo Lopes cross which broke the deadlock after 33 minutes.
Atletico Madrid drew 0-0 with Sevilla in a match between two sides who are expected to be fighting for a Champions League place by the end of the season.
The home side had the better openings but it will be a game remembered more for the number of fouls with the referee issuing eleven yellow cards.
Diego had a shot blocked by keeper Javier Varas and Jose Antonio Reyes missed the target with an excellent chance.
After the break Manu del Moral went close for Sevilla but Varas continued to save Sevilla while Radamel Falcao ballooned the best opportunity over the crossbar from inside the six yard box.