Joao Felix sent the Catalan outfit ahead in the 55th minute of the contest at Mestalla, but Hugo Guillamon levelled the scores in the 70th minute, and the points were ultimately shared in Spain's top flight.
Barcelona had 16 shots, eight of which were on target, but they were unable to score more than once, and Xavi rued his side's missed opportunities in the stalemate.
"This match pretty much sumarises the season for us. We train finishing but it depends on the players' confidence," Xavi told reporters during his post-match press conference.
"We have to be one of the teams with the worst finishing in Europe. I am very frustrated today.
"We deserved to win, we did everything. What happened over the past weeks with regard to effectiveness was repeated.
"The dressing room is upset and they are as disappointed as I am because we played a good game, and that was enough to win."
The result has piled more pressure on Xavi, with Barcelona now without a victory in their last three matches in all competitions, two of which have been defeats.
A recent report claimed that the club's president Joan Laporta had lined up Rafael Marquez as a replacement for Xavi, with the head coach coming under increasing pressure.
However, Barcelona midfielder Pedri insisted that the team are still behind their manager following the draw at Mestalla.
"We are with the coach, we are with Xavi," Pedri told reporters after the match. "We all have to be together to turn it around - that's the only way. We are together."
Barcelona are currently third in the La Liga table, boasting 35 points from their 17 matches courtesy of a record of 10 wins, five draws and two defeats.
The reigning champions are four points behind second-placed Real Madrid and six from leaders Girona, with the top two both having games in hand on the Catalan side.