Barca seemed all but out of the title race after conceding a last-minute equaliser to draw 2-2 at home to relegation-threatened Getafe last weekend.
However, leaders Atletico Madrid subsequently lost 2-0 away at Levante, whilst Real Madrid have drawn twice against Valencia and Valladolid in the past week to leave them in third place, four points adrift of Atletico with just two games to play.
Barcelona remain three points adrift of Diego Simeone's men themselves, but will win the league if they win their two remaining games away to Elche on Sunday and then when Atletico visit the Camp Nou on the final weekend of the season.
"We are in a better position today than we were a few weeks ago," said Messi.
"We can see that we have an opportunity to win the league. We need to take advantage of this moment and not let it escape."
Gerardo Martino's men are sure to face a tough task this weekend, though, as Elche are in need of points themselves as they sit just three points above the relegation zone and have yet to be beaten at home in nine league games so far in 2014.
Barca will again be without the injured Gerard Pique, Jordi Alba and Neymar, although all three are hopeful of being fit for the potential title decider against Atletico next weekend.
However, should Barca fail to win this weekend, Atletico can mathematically seal their first title in 18 years with victory over Malaga at the Vicente Calderon.
Atletico have injury worries themselves as top scorer Diego Costa looks set to miss out due to a hamstring injury, which could yet endanger his participation in the clash with Barcelona and in the Champions League final against Real Madrid on .
Diego Godin is also suspended for Los Rojiblancos, but right-back Juanfran returns from suspension having missed the defeat at Levante.
However, forward Adrian Lopez still believes home advantage should be enough to edge his side closer to the title.
"We know that we are very strong at home in front of our own fans," he said .
"It is a key game. With all that we are playing for to get three points on Sunday would be a huge step forward.
"We know the atmosphere will be incredible. The fans are going to be very excited having watched what has been a great season for us and it could end in a great and happy way for everyone."
David Villa is likely to replace Costa with Raul Garcia moving forward from the midfield role he has deployed in recent weeks to make space for the return of Arda Turan.
Real Madrid need to win away to Celta Vigo to maintain any hope of catching Atletico, but are likely to be without a host of first-team regulars, including Cristiano Ronaldo.
The current World Player of the Year limped off with a minor muscular problem less than 10 minutes into Real's 1-1 draw with Valladolid and is unlikely to be risked with the Champions League final against Atletico just two weeks away.
Pepe and Angel di Maria also picked up injuries against Valladolid, but Gareth Bale should return after missing the trip to the Jose Zorilla with a knock.
At the bottom, Osasuna could join Real Betis in being mathematically relegated should they lose away to Espanyol and any two of Getafe, Valladolid and Almeria win when they face Sevilla, Betis and Granada respectively.
Fixtures (all times 1700 GMT unless stated)
Villarreal v Rayo Vallecano (1800), Levante v Valencia (2000)
Athletic Bilbao v Real Sociedad (1500), Granada v Almeria, Real Betis v Valladolid, Espanyol v Osasuna, Celta Vigo v Real Madrid, Atletico Madrid v Malaga, Elche v Barcelona, Getafe v Sevilla