The Argentine superstar turned the game on its head following his introduction but a late goal from the Basque midfielder means that the title will not be decided this weekend
After the 4-0 mauling at the hands of Bayern Munich in midweek, Lionel Messi began from the bench but Tito Vilanova selected a strong team. However, the Basque side began the game impressively and deservedly took the lead into halftime with a goal from Markel Susaeta.
Messi was let loose after the break and after equalizing with a sublime individual effort he assisted Alexis Sanchez for what looked like the winner until Ander Herrera levelled the game in the final minute of normal time.
Bilbao pressed high from the outset and with six minutes played Gerard Pique was caught in possession on the right, deep in his own half. Herrera subsequently drifted into the box but his low cross was narrowly missed by the stretching Aritz Aduriz as he slid in at the back post.
The Blaugrana kept cool heads, though, and came agonizingly close to taking the lead in the 16th minute. Cesc Fabregas' delightful reverse pass fed straight into the path of Alexis' run, but his cross-goal shot from 20 yards came back off the frame of the goal.
The Catalan defense was not coping with the intensity of the game quite so well and with 28 minutes on the clock Marcelo Bielsa's men broke the deadlock. Aduriz beat Pique to the byline before driving the ball across the face of goal for Susaeta to tap in at the back post.
Aduriz should have doubled the Basques' advantage two minutes before the break after ghosting in between Pique and Eric Abidal but he could not keep his header down from Oscar De Marcos' cross.
Eleven minutes into the second half Barcelona nearly fell further behind as Susaeta hit the crossbar from a 20-yard free kick and Mikel San Jose sent his header from the rebound into the side netting.
Messi was quickly introduced in place of Xavi and while Barca instantly looked a better team, Pedro and Alexis were both unable to beat Iraizoz from inside the area.
But in the 67th minute Messi provided a majestic moment of individual brilliance as he wriggled between three players, ducking inside and out, before caressing the ball into the bottom corner to equalize.
Two minutes later the Argentine was involved again as the Catalans completed the turnaround, heading Dani Alves' cross into the path of Alexis who spun and fired the ball between Iraizoz's legs.
But victory for the visitors was not to be as Adriano failed to clear a cross from the left and the loose ball was rifled into the bottom corner by Herrera.
A draw means that Barcelona cannot be crowned as champion this weekend and must instead turn its attention back to a daunting Champions League tie in midweek.