Messi's opener needed a huge slice of luck, as he was wrongly not flagged offside from Ivan Rakitic's through ball before blasting into the top corner.
The No 10 doubled the lead shortly before half-time from close range after a ricochet in the penalty area had fallen into the path of Jordi Alba, and completed his treble just after the hour.
"They are three important points because they allow us to take advantage of our direct rivals slipping up, but of course, it is only the third match of the season". It had tied Valencia 2-2 last weekend.
Atletico Madrid also trail Barca by four points as without the suspended Antoine Griezmann they drew a blank in an intense 0-0 draw at Valencia. Diego Simeone's team has played three straight away games before being able to inaugurate its Wanda Metropolitano Stadium on Saturday against Malaga.
Barcelona have two out of two wins in this new season of the La Liga.
Nasa captures the strongest solar flares of the past decade
The path of the solar flare's CME is now being modelled to see whether some of the material could impact our atmosphere. M-class flares are medium-sized; they generally cause brief radio blackouts that affect Earth's polar regions.
Athletic Club Bilbao moved into a privileged position into the table with a 2-0 win over a tough to beat Girona.
Maxi Gomez scored a first-half victor in Vigo.
Aritz Aduriz scored his 150th goal for Athletic in the second half after Iker Muniain opened the scoring with a smart finish from an Inaki Williams cross in the 25th minute.
Villarreal conceded early but recovered to defeat Real Betis 3-1 and earn its first victory.
Valverde, speaking about Messi's impact for the team in their match with Espanyol said in a post-match news conference: "I am happy for Leo who scored three goals and is extraordinary".
- 10 militants dead, nine Egyptian policemen wounded in Cairo shootout
- NJ's Menendez Set for Rare Senate Corruption Trial
- European court to review $1.3B fine against Intel
- Netflix Offered for Free on T-Mobile's Unlimited Family Plan
- Nebraska Preview: Cornhuskers at Oregon
- Tower Crane Spins As Irma Outer Bands Hit Miami
- Tropical storm Jose in Atlantic upgraded to hurricane
- Facebook Says Sold Political Ads To Russian Company in 2016 Election
- Oklahoma Face Difficult Road Test Against Ohio State
- Pressure mounts on boss De Boer after loss at Burnley