La Liga underdogs Las Palmas handed leaders Barcelona their first loss of the La Liga season on Saturday, spoiling the Catalan giant's 125th anniversary celebrations in the process.
Sandro Ramirez sent Las Palmas ahead early in the second half and although Raphinha hammered home an equalizer, Fabio Silva struck to claim three points and take his team up to 14th.
Barcelona still lead champions Real Madrid by four points but third-place Los Blancos, who host Getafe on Sunday, have played two fewer games than the Catalans and Atletico.
Barca have now gone three league games without a victory, after a run of 11 wins in 12 prior in the top flight.
"We had a bad game, we have to look at what we're doing badly to try and improve and win games," Raphinha told Movistar.
"I don't care about my goal, I care about winning, we didn't win and I'm not satisfied with the game."
Barcelona wore white shorts as part of their anniversary celebrations, as they used to back at the start of their history.
They held a gala in the city Friday night to mark the occasion, having been founded on Nov. 29, 1899, but came undone Saturday afternoon.
"We have to (play) like we did at the beginning of the season ... it's a big disappointment today," Flick told reporters.
"Today, we have more than 70% ball possession but we're not able to score the goals – maybe we have to change one or two things.
"We made some mistakes, but it was not the back four, it starts (with the players) in front, we have to speak about that."
The Catalans were able to name teenage starlet Lamine Yamal on the bench after recovering from an ankle problem.
Raphinha came closest to breaking the deadlock in the first half, scoring from an offside position and hitting the crossbar after being played through by Gavi.
Flick threw on Yamal at the break, hoping the winger would give Barca the advantage after an even first half.
Las Palmas took a surprise lead early in the second half when Kirian Rodriguez played in Ramirez, who drilled home from the edge of the box.
Raphinha hit back quickly for Barcelona with a thumping long-range effort, but Las Palmas were soon ahead again.
Silva ran onto Munoz's probing long ball and fired past Inaki Pena to restore the Canary Islanders' advantage with his fifth goal in eight league matches.
Former Barca goalkeeper Jasper Cillessen made several good saves and Las Palmas survived eight minutes of stoppage time.
"It was a very important win, we worked hard for it, Barca put you under a lot of pressure," midfielder Moleiro told Movistar after Las Palmas sealed their first away win at Barcelona since 1971.
Atletico Madrid romped to a five-star victory at bottom side Real Valladolid, with Antoine Griezmann scoring one of the goals of the season.
Diego Simeone's team have won seven consecutive games across all competitions and moved two points clear of champions Real Madrid.
Clement Lenglet opened the scoring after 25 minutes and Julian Alvarez added the second.
Rodrigo de Paul swept home the third before halftime and Griezmann produced a wonderful turn and finish soon after the break to add the fourth on a memorable night for the Rojiblancos, which even some home fans applauded.
Alexander Sorloth wrapped up Atletico's thumping victory in stoppage time.
Griezmann's goal saw the French forward exchange passes with Alvarez before executing a sensational turn and beating goalkeeper Karl Hein with a delicate touch.
"I have to thank (the Valladolid fans), in the end it's what all players want, we want people to enjoy it with us, whether it's opposition fans or our own," Griezmann told DAZN.
"In the end I have to be grateful for this love, I'm doing really well and I hope to give more."
Atletico beat Sparta Prague 6-0 in the Champions League on Tuesday, meaning Simeone's side scored 11 goals this week without reply.
"There are always things to improve, the team is always looking to do better," Simeone told DAZN.
"We have to keep our humility, the nobility of keeping on looking for more ... in the second half we could have done more ... but I'll stick with what the team's giving me, with humility you can do anything."
