Aston Villa ruined Tottenham's bid to climb back into the Premier League's top four as a costly mistake from Hugo Lloris condemned the north Londoners to a damaging 2-0 defeat on Sunday.
Playing for the first time since France's World Cup final defeat against Argentina, Tottenham goalkeeper Lloris weakly spilled Douglas Luiz's shot early in the second half and Emiliano Buendia pounced to put Villa ahead.
Lloris was left on the bench for Tottenham's draw against Brentford on December 26 as he rested after France's agonising final loss in Qatar.
The 36-year-old, who conceded three times against Argentina before France lost on penalties, might have wished he had been given longer to recover after his blunder against Villa.
Brazilian midfielder Luiz added Villa's second goal in the closing stages, leaving Antonio Conte's side to endure jeers from frustrated fans at the Tottenham Hotspur Stadium.
Tottenham had hoped the first Premier League match of 2023 would serve to kick-start their bid to qualify for next season's Champions League via a top four finish.
Instead, they suffered a New Year's Day hangover as mid-table Villa punished a lethargic display.
Fifth placed Tottenham have failed to win both of their matches since the World Cup break, a dip in form which has allowed fourth placed Manchester United to climb two points above them.
Adding insult to injury for Tottenham, it was former Arsenal boss Unai Emery who masterminded Villa's success on his return to north London.
Villa manager Emery, dismissed by Arsenal in 2019, has now won three of his four Premier League matches since replacing the sacked Steven Gerrard in November.
Son Heung-min started the match once again wearing the mask he used during the World Cup to protect his fractured eye socket.
But Tottenham's South Korean star ripped the mask off for good early in the first half, discarding it angrily after failing to control a pass.
Son's frustration summed up Tottenham's spluttering performance.
No player has scored more Premier League goals on New Year's Day than Harry Kane's five.
But the Tottenham striker was denied another at the start of the year when he nodded Ivan Perisic's cross goalwards, only to see Ashley Young clear off the line with an agile diving header.
Although Tottenham dominated possession for long periods, they couldn't make the breakthrough.
Villa hit them with a sucker punch five minutes after half-time as Lloris's blunder allowed the visitors to snatch the lead.
Luiz's long-range shot lacked the power to beat Lloris, but the keeper failed to hold it and Ollie Watkins pounced on the loose ball, flicking it to Buendia, who slotted home from 10 yards.
It was the seventh successive Premier League game in which Tottenham had conceded the first goal.
Perisic couldn't convert a golden opportunity to equalise when he fired over from Son's free-kick, while Kane miscued a decent chance from just inside the area.
Reprieved by those misses, Villa delivered the knockout blow in the 73rd minute.
John McGinn's superb pass split the Tottenham defence and Luiz took a touch before guiding a clinical finish past Lloris.