Messi penalty edges Catalan derby, moves Barca top
The Argentine scored the only goal of the game 14 minutes from time at Cornella El Prat after Javi Lopez was adjudged to have handled inside the area.
Espanyol were then reduced to 10 men when goalkeeper Kiko Casilla saw a straight red card for blocking Messi's goalbound effort with his hands outside the area.
Victory moves Barca two points clear of Atletico Madrid and five ahead of Real Madrid with both sides from the capital in action later on Saturday against Athletic Bilbao and Rayo Vallecano respectively.
"Derbies are always the same and you have to win them," said a relieved Barca boss Gerardo Martino.
"It doesn't come easy and they are always tight games, for that reason this was a risky away game for us and we value the three points even more."
Barca now firmly have the destiny of the title in their own hands as they host Atletico on the final day of the season.
However, the Argentine is taking nothing for granted after suffering a shock defeat to relegation threatened Valladolid earlier this month.
"What is left continues to be very difficult and very important. We still have seven finals left between now and the end of the league season and in those games we will also have with us the memory of our defeat in Valladolid."
- Messi's 36th goal of season -
The visitors started brightly and would have been in front had their star forwards been at their best as both Neymar and Messi wasted good headed chances when well placed inside the area.
Neymar then missed a glorious opportunity on 19 minutes when he blazed Dani Alves' cross over from point-blank range with an open goal to aim at.
Pizzi was next to pass up a wonderful chance as just two minutes later he fired over with just Jose Manuel Pinto to beat from Sergio Garcia's inviting cross.
Javier Mascherano was lucky not to concede a penalty as he appeared to catch Javi Lopez with a stray arm as the Espanyol full-back broke into the box.
Neymar came close to breaking the deadlock once more before the break as he prodded Jordi Alba's through ball beyond Casilla but the ball rolled passed the far post.
There was far less in the way of goalmouth action in the second-half, but Barca upped the pressure as Espanyol started to tire in the final 20 minutes and Gerard Pique struck the crossbar from Sergio Busquets' flick-on.
Moments later Martino's men did get the all-important goal as Lopez handled whilst contesting a cross with Neymar at the far post and this time referee Clos Gomez did point to the spot.
Messi stepped up and, just as in scoring twice from the spot in Barca's 4-3 win over Real Madrid last weekend, showed no sign of nerves as he calmly slotted home his 36th goal of the season.
Espanyol finished the game with 10 men as Casilla then saw red for handling outside the area as he blocked a lob from Messi that appeared to heading goalwards.
Lopez ended an eventful afternoon by going in goal as the hosts had already made all three substitutions and made a fine save in stoppage time to prevent Alexis Sanchez doubling Barca's lead.
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