Tottenham Hotspur 1, Monaco 2
Tottenham manager Mauricio Pochettino accused his team of lacking passion and refused to blame a temporary switch to Wembley after their return to the Champions League following a five-year absence ended in defeat on Wednesday night.
First-half goals from Bernardo Silva and Thomas Lemar earned French league leaders Monaco a surprise win in front of a record-breaking crowd, despite Toby Alderweireld heading Spurs back into the contest.
Pochettino castigated the hosts for the sloppy defending that saw them slip straight to the bottom of Group E but rejected suggestions, given weight by opposite number Leonardo Jardim, that playing in an unfamiliar setting had been a hindrance.
"No, that is to put an excuse. Football is on the pitch," said Pochettino.
"We need to improve and learn that we can't concede the goals that we conceded.
"We need to be more aggressive in possession, when we have the possibility to score we need to be more aggressive, and we need to show more hunger and more passion. I think we showed a lack of passion today.
"We wait a lot to play the Champions League, we fight a lot last season to be here, and your feeling is 'why don't we do more?'."
Jardim suggested Wembley's greater surface area than White Hart Lane might have made it more difficult for Tottenham to play their normal game.
He said: "Tactically, that this is bigger pitch than Tottenham's home may have affected them negatively as they play a pressing game and it's harder to close people down as there is more space."
Tottenham's first Champions League fixture since a last-16 elimination by Real Madrid in 2011 drew 85,011 fans to Wembley, their European base for this season, marking a record home crowd for an English club.
Home fans expecting a repeat of last season 4-1 victory at Monaco in the Europa League were given early cause for optimism when Spurs carved out chances for Son Heung-Min and Dele Alli in the first 15 minutes.
Son's hesitant shot was cleared off the line by Andrea Raggi while Alli's was smothered by Fabinho, and it was the Brazilian midfielder who set up the opening goal seconds later by charging down Erik Lamela's attempted clearance.
That freed Silva to run at Tottenham from the right and he slalomed past Jan Vertonghen before curling a left-footed shot past Hugo Lloris.
The Ligue 1 leaders hit Spurs on the break again after half an hour, livewire youngster Lemar volleying into the roof of the net from close range after Vertonghen missed Tiemoue Bakayoko's cross and the ball fell kindly.
Kamil Glik almost struck a killer third goal when his header looped wide from a free-kick; instead it was Spurs and Alderweireld who made a set-piece pay, the Belgium defender crashing Lamela's corner in just before half-time.
The introduction of Mousa Dembele at the interval gave Tottenham belated control of the midfield, and the second period became a glorified attack versus defence exercise in which Kane too often let Monaco off.
The England forward, who ended an nine-match drought on Saturday against Stoke, wasted one chance by hesitating and then shot tamely at Subasic after excellent hold-up play and a lay-off from substitute Vincent Janssen.
Monaco boss Jardim said his team's preparations had centred on trying to emulate their 3-1 victory at Arsenal in this competition two seasons ago.
"Mentally we tried to think back to how we were emotionally on the night we played so well and won against Arsenal at the Emirates," he said.
"Similar surroundings: a big stadium, packed, against a tough side. So that's what we drew upon for this game."