Jordi Alba's late equaliser maintained Barcelona's four-point lead over Valencia at the top of La Liga in a 1-1 draw at Mestalla on Sunday overshadowed by the league's lack of goal line technology. Lionel Messi's first-half effort clearly crossed the line, but wasn't allowed to stand as, unlike other major European leagues, La Liga has refused to introduce the technology on cost grounds. Rodrigo's opener on the hour mark rubbed salt into Barca's wounds, but the visitors responded when Messi picked out Alba eight minutes from time to ensure both sides remain unbeaten in La Liga.
However, just a second slip up from Barca this season does allow Real Madrid and Atletico Madrid to close to within eight points of the leaders.
"It was a monumental error by the referee," Alba told Movistar.
"Even I could see it was in from the middle of the pitch. We saw the replay at half-time and it's clear."
La Liga does, though, intend to introduce video assistant refereeing (VAR) for controversial decisions next season.
"VAR is something which will help football and will stop moments like this happening," added Alba.
Gerard Pique's absence at the heart of the Barca defence through suspension meant a first La Liga start for Thomas Vermaelen in nearly two years.
However, Valencia failed to expose any fragility in the visitors' backline in the first 45 minutes as Barca dominated the ball without creating too many clear-cut chances.
Indeed, the first half left only one clear talking point when Messi's low shot slipped through Valencia 'keeper Neto's legs and over the line, only for referee Ignacio Iglesias Villanueva to wave play on.
"It is a shame that these situations still arise," said Valencia assistant boss Ruben Uria, who took control from the sidelines with Marcelino Garcia Toral serving a touchline ban.
"We are in favour of technology and this time it has fallen in our favour."
Handed a huge let off, Valencia regrouped at the break and posed a far greater threat in the second period.
Simone Zaza dragged a shot just wide and Goncalo Guedes finally tested Marc-Andre ter Stegen for the first time from a narrow angle 58 minutes in.
Valencia had to wait just two minutes more to break the deadlock with Paris Saint-Germain loanee Guedes again heavily involved as he freed Jose Gaya down the left and his low cross was turned home by Rodrigo.
Messi finally put pen to paper on a lucrative new deal on Saturday, tying him to Barca till 2021, and the Catalans' dependence on the Argentine to produce a spark in the final third was clear as they chased the game in the final half-hour.
However, it was an off-colour Luis Suarez who had Barca's first attempt to get back on level terms as Neto parried away the Uruguayan's volleyed effort from the edge of the area.
Inevitably, Messi was at the heart of Barca's equaliser, though, as he picked out Alba with a sumptuous lofted pass for the former Valencia left-back to volley home.
It was Valencia who had the better chances to win the game in a thrilling finale as on-loan Manchester United midfielder Andreas Pereira fired into the side-netting.
And with virtually the lack kick of the game Zaza volleyed over when unmarked at the back post.
Earlier, Sevilla produced their second stunning comeback in five days by overcoming a 2-0 half-time deficit to win 3-2 at Villarreal on Sunday.
In the first match since the club confirmed Sevilla boss Eduardo Berizzo had been diagnosed with prostate cancer, Villarreal's players and fans showed their support for the Argentine before kick-off.
And just as in midweek against Liverpool when Sevilla came back from 3-0 down to snatch a dramatic late draw, goals from Clement Lenglet, Franco Vazquez and Ever Banega snatched all three points after Cedric Bakambu and Carlos Bacca had given Villarreal the lead.