Barcelona: La Liga leaders Barcelona were held to a 2-2 home draw by Celta Vigo on Saturday as their former assistant coach Juan Carlos Unzue dented their title hopes, while Atletico Madrid took advantage by coming from behind to beat Real Sociedad 2-1.
Celta striker Iago Aspas silenced the Nou Camp by putting the visitors ahead in the 20th minute, knocking in on the rebound after splitting the home defence with a darting run through the middle.
Lionel Messi quickly replied at the other end, finishing off a sweeping team move two minutes later to score for the first time in six games in all competitions and net his 13th league goal of the season.
Luis Suarez had a goal wrongly ruled out for offside before the break, the second time Barca have cursed their luck with referees in a week after Messi was denied a clear goal in the 1-1 draw at Valencia when his shot had clearly gone over the goal-line.
Messi helped set up what looked to be the winning goal for Suarez in the 62nd minute as the striker thrashed home a Jordi Alba cutback but Barca were denied victory by another Uruguayan striker in Maxi Gomez.
He slotted in from close range after another searing run by Aspas, who capitalised on Barca defender Samuel Umtiti injuring his hamstring as he tried to keep up with the Spanish forward.
The France international is in danger of missing the "Clasico" against champions Real Madrid on December 23 after Valverde said he believed the player had torn the muscle.
"The injury cost us the goal, it was an accumulation of catastrophes, because of the draw and the injury," the coach told a news conference.
"Losing Samuel right now is a big loss, he was in excellent form."
Barca bombarded Celta's area in the remaining 20 minutes, with Gerard Pique hitting the near post from close range, but could not avoid dropping points for the second game in a row for the first time this campaign.
"We kept trying to win the game and had chances to do that. We have dropped two points but this is nothing that hasn't happened before," Valverde added.
Barca still lead the standings with 36 points but second-placed Valencia can cut their deficit on the leaders down to two if they beat Getafe on Sunday.
Atletico moved to within six points of Barca thanks to an 88th minute winner from Antoine Griezmann after Filipe Luis had cancelled out Real Sociedad forward Willian Jose's first half penalty in the 63rd.
Griezmann, who came through the academy at Real Sociedad before being sold to Atletico for 25 million euros ($30 million) in 2014, slid in at the far post to nudge in Saul Niguez's header and keep Atletico's title hopes alive, but chose not to celebrate the goal.