Tottenham Hotspur's top-four ambitions suffered a blow as they lost 4-2 at Brighton & Hove Albion in the Premier League on Thursday.
A late rally saved them from their heaviest defeat since Ange Postecoglou became manager this season.
Victory would have put injury-hit Spurs above Manchester City into fourth spot but they were mauled on the south coast as a Brighton side also missing key players ran riot.
A powerful early strike by Josh Hinshelwood and Joao Pedro's penalty gave the hosts a deserved 2-0 lead at halftime as Tottenham struggled to deal with Brighton's intensity.
The visitors responded in the second half with Richarlison having a goal disallowed but when halftime substitute Pervis Estupinan sent a thunderbolt past Spurs keeper Guglielmo Vicario and Joao Pedro netted a second penalty the game seemed over.
However, Tottenham's late substitute Alejo Veliz fired home from close range in the 75th minute and Ben Davies scored with a header making a miraculous comeback suddenly look possible.
Midfielder Pierre-Emile Hojbjerg hit the post for Spurs in stoppage time as Brighton looked nervy but they held on to move into eighth place in the table on 30 points while Tottenham remain fifth on 36, a point off the top four.
The final scoreline hardly did justice to a chaotic match in which Tottenham were second-best for long periods but showed some spirit to emerge with their pride intact.
However Brighton, without the likes of winger Kaoru Mitoma, Tariq Lamptey, Solly March and Julio Enciso, were worthy winners as they snapped a three-match league sequence without a win.
"It is a very disappointing performance. This is not how we've approached the season," Spurs captain Son Heung-min said.
"This performance was nowhere near the level we want to play at. But now is not the time to point fingers at each other because the games are coming fast."
Tottenham host in-form Bournemouth on Sunday when they will be without Kulusevski who will be suspended after picking up another booking, while Brighton visit West Ham United on January 2.
Tottenham's defensive problems, made worse by Argentine centre back Cristian Romero having been added to their long injury list, were exposed by Brighton as the hosts dominated the first half with some slick, high-intensity football.
Vicario had already made two fine saves before Hinshelwood was played in by Joao Pedro on the edge of the area and thumped an unstoppable shot high into the net.
Brighton almost doubled their lead when Jan Paul van Hecke's header hit the post and as the ball rebounded towards Danny Welbeck the striker was blatantly pulled back by Dejan Kulusevski with a penalty being awarded after a VAR check.
Joao Pedro rolled the 23rd-minute spot kick past Vicario to put Brighton in command although Richarlison nearly responded just before halftime with a shot that kissed the post.
Spurs looked brighter after the break and wasted several chances before Brazilian Richarlison netted, only to have his joy cut short as VAR showed he was offside.
Estupinan made it 3-0 with a sensational strike from outside the area before Tottenham substitute Giovani Lo Celso conceded a penalty that Joao Pedro dispatched.
A raft of substitutions revived Spurs with Bryan Gil and Veliz adding some energy to the visitors and the latter celebrated wildly as he slotted his first goal for the club.
Davies headed in from close range and Tottenham then had numerous chances to try to grab an unlikely point although they can have no real complaints about leaving empty handed.