An injury-plagued Barcelona moved into first place with 14 points as Adriano gave them their first away win of the season.
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.
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.
Levante had Juanlu Gomez to thank for their 1-0 win over former leaders Real Betis, their fourth successive victory. (The News Pk)