Lionel Messi's 19th straight scoring effort in the Spanish league wasn't enough to stop Barcelona from drawing 2-2 at Celta Vigo, as the leaders stumbled on Saturday before their Champions League quarterfinal with Paris Saint-Germain.
Real Madrid, meanwhile, also sputtered to a 1-1 draw at Real Zaragoza despite Cristiano Ronaldo's goal, while Malaga won 3-1 at Rayo Vallecano with both teams also facing first legs in Europe's final eight this week.
Barcelona appeared to have secured the win when Messi added to his earlier assist to Cristian Tello by scoring in the 73rd minute to extend his record league scoring run to 19 consecutive games. With the goal against Celta, Messi has netted against every other team in the league during the streak.
But Barcelona's defence left midfielder Borja Oubina unmarked to head home the tying goal two minutes from time, reawakening doubts about its injury-riddled backline before Tuesday's trip to PSG.
"What Leo is doing is an unheard of feat in the league's history and it shows the importance he has and his greatness as a player," said Barcelona assistant coach Jordi Roura. "With time, we will give him even more credit for what he does.
"We weren't thinking about Tuesday. This league is of utmost importance for us. We just lacked a little bit of concentration at the end."
The draw didn't endanger Barcelona's campaign to reclaim the league crown. The Catalan club maintained its 13-point advantage as Madrid seemingly had its sights set on Wednesday's game against Galatasaray in the Champions League.
Elsewhere, midfielder Pedro Morales scored one goal and set up two more in his first start for Malaga to give it a convincing victory at Rayo before the Costa del Sol side hosts Borussia Dortmund, also on Wednesday.
Morales served up passes for headed goals by Weligton in the 21st and Julio Baptista in the 55th before he capped his fine performance since joining from Dinamo Zagreb in January with a long-range strike four minutes from time.
After a long international break and with the PSG game looming, Roura rested several of his regular starters, while 21-year-old Martin Montoya and 22-year-old Marc Bartra were picked to patch up Barcelona's depleted defence with Carles Puyol, Jordi Alba, and Adriano all out with injuries.
Messi, making his first start as Barcelona captain in league play, was forced into a playmaking role with Xavi Hernandez injured and Andres Iniesta only playing the final 25 minutes.
Barcelona dominated possession throughout, but Celta struck first after the visitors lost possession in their half, leading to midfielder Nacho Insa receiving Fabian Orellana's short pass that he poked just inside the upright in the 38th.
Messi cued up Tello to pull Barcelona level five minutes later with a lobbed pass to beat Celta's flimsy offside trap, with Tello curling the ball with a right-footed shot around the goalkeeper and off the base of the far post.
Roura sent Iniesta on and striker David Villa followed three minutes later as Barcelona sought the winner.
With Villa up front, Messi had more room to manoeuvr and he soon played Tello wide on the left flank before sliding forward to meet his return cross and drive it in with a low left-footed strike.
Messi has a league-leading 43 goals through 29 rounds and 56 overall this season. He has 30 goals during his unprecedented run of scoring in 19 straight rounds, shattering the previous mark of 10 straight games.
Celta, which was fighting to escape the relegation zone, made one last desperate push, and it paid off when Dani Alves failed to check Oubina at the far post to turn in Orellana's cross.
"In the second half we played our best football and just when we thought we had the three points, they got away," Tello said.
Eric Abidal, who was named to Barcelona's squad for the first time since receiving a liver transplant last year, never left the bench.
Barcelona head coach Tito Vilanova didn't travel with the team after returning this week from a 10-week medical stay in New York where he received treatment after the removal of a throat tumour in December. He may accompany the team on Tuesday.
Zaragoza, which entered the match hovering over the drop zone without a win in its last 11 games, went out the more energized side, and Rodrigo "Rodri" Rios scored six minutes in after Madrid's Luka Modric lost the ball. Ronaldo pulled Madrid even in the 38th.
Levante plays Sevilla later.
On Sunday, it's: Valladolid vs. Osasuna, Mallorca vs. Deportivo La Coruna, Espanyol vs. Real Sociedad, and Atletico Madrid vs. Valencia. Real Betis hosts Getafe on Monday, while Granada visits Athletic Bilbao.