Ange Postecoglou was left to rue a "painful" collapse as Tottenham squandered a two-goal lead to lose 4-3 against Chelsea on Sunday.
Dominic Solanke and Dejan Kulusevski both profited from Marc Cucurella slips to fire the hosts 2-0 up after just 11 minutes at the Tottenham Hotspur Stadium.
Jadon Sancho pulled one back, however, with a delightful 17th-minute drive before Tottenham wilted under pressure in the second half.
A pair of Cole Palmer penalties, scored either side of Enzo Fernandez's lashing finish to put Chelsea 3-2 up, proved the undoing for Postecoglou's side.
Spurs, who grabbed a late third through Son Heung-min, suffered a second defeat in the space of three days after a midweek loss to Bournemouth, though Postecoglou believes the performances were contrasting.
"It's a sore one for sure, it's painful," the Tottenham boss told Sky Sports. "We started the game really well and then we lose Cristian Romero and we had to reshuffle.
"We still had some big moments to get a third and finish it off. The second half was a ding-dong for long and then they scored. The two penalties weren't great, we need a bit of discipline in the box.
"It's a key point when you lose a key player in the first 20 minutes, He couldn't continue so it's not ideal.
"We didn't play well in midweek but we did here. They're a top side, you have got to give credit to them. We got distracted in key moments.
"We need to realise we are tough to stop when we do play our football. The two penalties were poor. When you're playing these top teams, the momentum shifts quickly."
Yves Bissouma fouled Moises Caicedo for the first penalty, with Pape Sarr at fault for a challenge on Palmer for the second spot-kick.
Tottenham felt aggrieved Caicedo was still on the pitch, though, as the Chelsea man survived a VAR review for a first-half lunge on Sarr that could have been deemed worthy of a straight red card.
"I haven't seen the replays. I thought a couple of decisions were poor," Postecoglou said of the Caicedo decision. "We have to accept it and move on."
Micky van de Ven and Romero returned for Sunday's clash, though the latter was forced off after just 15 minutes before his centre-back partner came off in the closing stages.
"He felt a bit tight," Postecoglou said of Van de Ven. "He was only meant to play 60 or 70 minutes. Hopefully it's not too bad because you could see the difference.
"I'm hoping Romero isn't too bad. We're thin on numbers and if we're thin in January, we'll be looking to add to the squad because they need some help."
Sunday marked the 11th time that Tottenham lost a Premier League game after having been two or more goals ahead – at least four more such defeats than any other side in the competition's history.
It was also the first time they did so at home in the league since September 2001 against Manchester United in a 5-3 defeat.
Son shared a similar frustration to Postecoglou, though wanted to shoulder the blame for his missed chance at 2-2 when one-on-one with Robert Sanchez.
"It's very disappointing. I don't know what to say at the moment," Son told Sky Sports. "We can't concede goals like this. We can't dive into this situation.
"I can stay here all day talking about the mistakes but I'd rather blame me with the chance and I'd rather take the blame.
"We have got to stick together in such difficult moments, it's very important and it's why we need big support. The players are very young and they need support more than before and more than we had.
"The fans were always supporting amazingly but I think it's time the players also need to step up. We need some big support and big cheering up."
In Postecoglou's 53 Premier League games in charge, Tottenham have both scored and conceded in 36 of them (68%).
Of all managers to oversee 50+ matches in the competition's history, only Ossie Ardiles' games had a higher ratio of seeing both sides score (69% - 37/54).