Lionel Messi's stunning free kick secured Barcelona a last-gasp draw, but failing to win at Villarreal was a damaging result given LaLiga leaders Real Madrid's indomitable form.
Zinedine Zidane's side equalled Barca's Spanish record of 39 games unbeaten in all competitions by swatting aside Granada on Saturday.
Barca needed to respond at Villarreal but could only muster a 1-1 draw, with Messi's superb free-kick cancelling out a fine second-half Nicola Sansone strike.
The Argentinian magician may have prevented the Yellow Submarine winning this fixture for the first time since 2008, but it continued a disappointing start to the year for Luis Enrique's side.
Fresh from the midweek Copa del Rey loss at Athletic Bilbao, the draw at Villarreal leaves them third in the standings -- a point behind second-placed Sevilla and five off Real Madrid, who also boast a game in hand.
The disappointment of Messi's late goal was compounded for Villarreal by Jaume Costa's stoppage-time sending off.
This match was the first at the renamed El Madrigal after it was announced in the build-up that the stadium would now be called Estadio de la Ceramica after one of the symbols of Castellon.
It was a new chapter that almost got off to a dream start, with ex-Barca midfielder Jonathan dos Santos firing just over.
Alexandre Pato was causing problems on the flank as the first half wore on and Sansone got a shot away on the counter, but it was far from one-way traffic.
Villarreal were having to defend resolutely and Neymar, already frustrated a couple of times, came close when allowed the chance to fizz a shot just wide from the edge of the box.
A last-ditch challenge thwarted the Brazilian as Enrique's men continued to threaten a goal late in the first half, with Messi meeting a corner into the box with a glancing header that forced Sergio Asenjo into action.
Lucas Digne, impressing at left-back, cutback smartly for Luis Suarez to get a shot on target ahead of the break -- from which Villarreal returned strongly.
Barcelona gave away possession cheaply and the hosts broke from deep. Pato burst through the middle and laid off a lovely ball that Sansone impressively struck low across Marc-Andre ter Stegen.
It was a 50th-minute gut punch that Barca could have cancelled out straight away had Neymar produced a better shot after Villarreal were caught out by a quickly-taken Messi free-kick.
Javier Mascherano sent an unorthodox header over as Barca pushed for a leveller, which they felt they should have had a chance to score from the spot after captain Bruno threw a hand at a Messi shot in the 72nd minute.
The Argentinian was frustrated again moments later after superbly striking the post as the match heated up, with penalty appeals at both ends.
Asenjo denied Suarez and then saw Neymar send an overhead kick over, before substitute Arda Turan missed a header and the hosts defence was disrupted by a wrist injury to Mateo Musacchio.
But it looked like Villarreal would hold out for a memorable win, only for Messi to underline his class by beautifully firing an unstoppable free-kick into the top left-hand corner.
To make matters worse for Villarreal, impressive full-back Costa was sent off for a second booking at the death.