Barcelona must wait at least another week to wrap up the title after they conceded a late goal in a 2-2 draw at Athletic Bilbao in La Liga on Saturday.
Victory for Barca and defeat for second-placed Real Madrid at city neighbours Atletico in the later kickoff (1800 GMT) would have given the leaders an unassailable 16-point advantage over their great rivals with five matches left.
However, Real now have a chance to trim the gap to 11 points although they are missing injured top scorer Cristiano Ronaldo for the trip to the Calderon.
Athletic, without a win in six La Liga games against Barca at their San Mames stadium, took a surprise 27th-minute lead when Aritz Aduriz crossed for Markel Susaeta to finish from close range.
Barca huffed and puffed in search of an equaliser but were fortunate not to fall 2-0 behind when Susaeta struck a free kick against the crossbar 10 minutes into the second half.
Only when Argentine forward Lionel Messi, who missed Barca's last three La Liga games with a hamstring strain, came off the bench on the hour did the Catalans rediscover their cutting edge.
The World Player of the Year brilliantly weaved his way past four defenders to equalise in the 67th minute and Alexis Sanchez, who earlier struck the post, made it 2-1 two minutes later.
Messi's goal, his 44th in 33 league matches this season, set another record as it took his tally away from home to 24, one more than the previous best set by Ronaldo last term.
Barca have also equalled their own La Liga record by scoring in 26 consecutive away matches.
They looked to have another three points safely in the bag before Bilbao midfielder Ander Herrera rifled a low shot into the corner of the net on 90 minutes to send the home fans into raptures on a wet and chilly evening in the Basque Country.
Barca may have another chance to wrap up the title next weekend when they play at home to Real Betis on Sunday after Real have hosted Real Valladolid on the Saturday.
In Saturday's earlier kickoff, Celta Vigo boosted their chances of avoiding relegation when they won 1-0 at Levante to climb out of the danger zone.
Photograph: Vincent West/Reuters