Spanish champions Barcelona fell to a damaging 2-1 defeat at Girona on Monday to leave them trailing Real Madrid by two points at the top of LaLiga.
Los Blancos beat Real Sociedad on Saturday to overtake the Catalans and Hansi Flick's side could not defeat Girona in an gripping derby clash to reclaim the lead.
Teenage star Lamine Yamal missed a penalty for Barcelona, who took the lead through defender Pau Cubarsi just before the hour mark.
However goals from Thomas Lemar and Fran Beltran helped Girona, 12th, mount an impressive comeback.
"In the end Girona deserved it, they had a lot of chances, we defended very badly," admitted Flick.
"We are not in a good mood, not in a good moment, I gave the team two days off because I think it's important they reset.
"There's a long way (to go), we're now in second, now we have to fight for first place in the table."
Barca were still licking their wounds after a heavy 4-0 defeat by Atletico Madrid in the Copa del Rey first-leg semifinal last week, and this defeat made things even worse.
"We have to improve because they can't score these two goals against us," Cubarsi told DAZN.
"We have to be self-critical, we didn't play a great game, we have to improve, but now we have to rest and charge our batteries."
Both sides were attacking with abandon in a very open first half and it was remarkable they went in goalless at the break.
Raphinha whipped a shot narrowly wide and Yamal fired straight at Girona goalkeeper Paulo Gazzaniga when through on goal.
At the other end Ukrainian striker Vladyslav Vanat missed a slew of presentable opportunities.
Ferran Torres fired a good chance wide for Barca and Raphinha drove against the upright as Flick's side pushed for the opener.
They should have got it when Dani Olmo was clumsily felled in the box by Daley Blind, but Yamal hit the post from the spot.
Barcelona eventually took the lead through Pau Cubarsi's header from Jules Kounde's cross after 59 minutes, but Girona swiftly pulled level.
Thomas Lemar slipped away from Eric Garcia and turned home Vanat's pass from close range.
It shifted the momentum in Girona's favour and Barca were left relying on some stunning saves from goalkeeper Joan Garcia to keep them afloat.
The stopper denied Ivan Martin and Vanat with a remarkable double save, and then thwarted Joel Roca with his leg.
CONTROVERSIAL WINNER
Barca could not stem the tide and Girona forced their way in front after 87 minutes, with Fran Beltran stroking home from the edge of the area.
The visitors, who last week made an official complaint to the Spanish football federation over perceived refereeing inconsistencies, were left fuming after Kounde was fouled by Claudio Echeverri in the build-up and it went unpunished.
"It seemed like a foul (on Kounde) to me, but we shouldn't focus on decisions we can't control," said Barca defender Gerard Martin.
Flick said "everyone saw" what happened and it was a "clear" foul, but he would not complain about it too much because Barca had a lot to improve on themselves.
"I would speak about that if we played well, but we didn't play well, so it looks like an excuse and complaining," said Flick.
"The (officials) do their job, sometimes it's not a good job, but they are on the same level as we played, so it's maybe not a good level."
Girona ended the game with 10 men when Roca scythed down Yamal to cut short a desperate Barca attack deep in stoppage time.
It did the job and the hosts celebrated wildly at the end with their jubilant fans at Montilivi, as Flick demanded explanations from the referee.
"Three points against Barca are more than three points, normally they beat almost all teams," said happy Girona coach Michel Sanchez.