Lionel Messi's 500th career goal couldn't prevent Barcelona suffering a third consecutive league defeat for the first time since 2003 as they opened the door to Atletico Madrid.
Luis Enrique's side were beaten 2-1 at home to Valencia and Atletico, who had already beaten Granada, now move level on points with the league leaders.
Both sides are level on 76 points, with Real Madrid a point further back after their 5-1 victory over Getafe.
Barcelona fell behind after just 26 minutes due to a Ivan Rakitic own-goal. Valencia doubled their tally on the stroke of half time through Santi Mina.
Lionel Messi reached a personal milestone recording his 500th career goal, ending a five-game goal drought, but it wasn't enough to see his side come away with nothing from the match.
"We’ve got a marvellous challenge, if we win the five games remaining we will be champions," Enrique said after the game.
"Of course, our credit has run out and we are aware of the challenge. We’re going to approach it like a Barça player always does, with our heads held high."
