Lionel Messi's stunning free-kick secured Barcelona a last-gasp draw, but failing to win at Villarreal was a damaging result given La Liga 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.
Athletic Bilbao were unable to feed off their superb win over Barcelona in the Copa del Rey, held to a 0-0 draw by Alaves.
Three days after beating Barcelona 2-1, despite playing the final minutes with nine men, Athletic failed to win again at home and stayed in seventh place.
It was 11th-place Alaves that came closest to scoring at San Mames when Victor Camarasa struck the left post with a right-foot shot from outside the area in the 36th minute.
Celta Vigo defeated Malaga 3-1 to jump into ninth place at the Estadio Balaídos.
Iago Aspas, Daniel Wass and Fontàs fired the hosts into a commanding 3-0 lead after 73 minutes, while a Daniel Wass own goal provided Malaga their sole consolation on the day.
Meanwhile, Real Betis cruised past Leganes 2-0 thanks to second-half goals from Ruben Castro and Cristiano Piccini.
Press Association contributed to this report.