Barcelona came from behind to beat Eibar 4-2 at the Nou Camp, but it was not enough to deliver the La Liga title in Luis Enrique's final home match.
Enrique's side needed leaders Real Madrid to slip up at Malaga to overtake them at the top of the table on the final day, but despite producing a second-half recovery, the hard-earned victory was not enough.
Japan midfielder Takashi Inui had fired Eibar into a shock early lead before doubling the visitors' advantage with a stunning half-volley just after the hour.
Barcelona, though, rallied following an own goal from Eibar defender David Junca and, after Lionel Messi saw his penalty saved, the hosts levelled through Luis Suarez.
Messi added another from the spot as Eibar were reduced to 10 men before slotting in a superb individual goal in stoppage time, but it was all to no avail.
As news of Cristiano Ronaldo's early goal at Malaga filtered through, the Nou Camp was left in stunned silence as Eibar took an unexpected lead after just seven minutes.
Full-back Ander Capa got forwards down the right flank and floated over a deep cross to the back post, where Inui arrived to crash the ball in off the underside of the crossbar.
Barcelona looked for a quick response, with Suarez stabbing the ball wide.
Suarez then thought he had equalised after 15 minutes when he slotted in a cross from Jordi Alba, but the assistant referee's flag was up for offside in the build-up.
Barcelona continued to press Eibar deeper, with Suarez firing a low shot goalwards from the edge of the penalty area which keeper Yoel Rodriguez pushed wide at full stretch.
There was, though, a massive let-off for the home side just before half-time.
Inui cut back inside from the left to drill in a low shot which Marc-Andre ter Stegen pushed out straight to Sergi Enrich. The Eibar forward could only stab the ball wide of an open goal, however, as Jordi Alba tried to make a last-gasp tackle.
At the start of the second half, Inui forced Ter Stegen into a save at the near post.
Eibar keeper Yoel then tipped away a low drive from Andres Iniesta before Messi fired wide.
As Real Madrid moved further ahead of Malaga, Barcelona fell further behind just after the hour.
A deep ball in from the right bounced up to Inui, who crashed a half-volley in off the underside of the crossbar
Barcelona were presented with a gift penalty with 20 minutes left, when Alba looked to have kicked the turf and fallen as he shaped to shoot, but the referee pointed to the spot - despite no Eibar player being near the defender.
Justice, however, was served when Yoel dived to his left to save Messi's spot-kick.
Barcelona eventually equalised on 73 minutes when Neymar's angled shot came back off the post and bounced on to Junca before rolling into the net.
Suarez then levelled matters when he turned in Paco Alcacer's flick-on from a corner after 73 minutes.
And the home side finally turned the match around two minutes later when Capa's sliding challenge brought down Neymar, which resulted in a penalty as well as a second yellow card for the Eibar defender.
Messi struck his penalty in the same place, low to Yoel's left, but this time the shot had enough power to beat the keeper for his 36th LaLiga goal.
The Argentina forward thought he had added another with a backheel finish from Andre Gomes' pass, but was flagged offside.
Yoel saved a one-on-one from Suarez, but could do little to prevent Messi scoring a brilliant 53rd goal of the season after running through the Eibar team from the halfway line.