The Lilywhites' patchy form continued in a seven-goal Tottenham Hotspur Stadium spectacular, where they were condemned to their second straight top-flight defeat despite leading 2-0 inside the opening 11 minutes.
Spurs suffered no fewer than three in-game blows in the derby, as Cristian Romero and Micky van de Ven - both of whom were making their comeback appearances after injuries - left the field prematurely.
Romero appeared to hurt himself while completing a backheel and had to be withdrawn for Radu Dragusin, and there were fears that Van de Ven had suffered a recurrence of his hamstring problem when he had to trudge off in the second half.
In addition, attacker Brennan Johnson did not look comfortable whatsoever as he made his way off the field eight minutes after the restart, although he appeared to be under the weather rather than nursing an injury.
Postecoglou most concerned about new Romero injury
Speaking to the media at full time, as quoted by football.london, Postecoglou expressed hope that neither Johnson nor Van de Ven's problems were serious, but he is still in the dark about the severity of Romero's issue.
"Romero is just obviously hugely disappointing. He felt something in his quad. He trained really well. He wasn't the one I was worried about, to be honest, but, you know, it's just like I said, the way the season's going for us unfortunately. So we just have to wait and see," Postecoglou said.
"The plan was always for Micky to play 60/70 today. Obviously, I thought Romero would be okay to play 90, but Micky, probably 60/70. So we were always going to take him off. He didn't feel anything significant. He just felt tightness, but we were always going to take him off anyway.
"Brennan just didn't feel well. He didn't feel well at half-time, but he wanted to give it a go, but he just wasn't feeling 100% so I had to take him off."
Asked if he 'gambled' with starting Romero and Van de Ven so soon after their recent issues, Postecoglou added: "No, Romero didn't injure the same thing. It's a totally different injury, but also people I'm sure are aware of our situation.
"It's not like I've got a multitude of options there, so, you know, you've got to make these decisions. Both players trained and tried well, and they both wanted to help. So you make these decisions with all the best information. Like I said, it's not like Romero re-injured his toe, it's a totally different injury, which could happen at any time."
Postecoglou: 'A couple of decisions went against us'
Tottenham exploded out of the blocks against their London rivals in Sunday's headline act, as Dominic Solanke and Dejan Kulusevski sent Postecoglou's men two goals to the good before Jadon Sancho pulled one back for the Blues.
However, two clumsy challenges from Yves Bissouma and Pape Sarr allowed Cole Palmer to net two record-breaking penalties either side of an Enzo Fernandez volley, as Chelsea completed a captivating comeback in North London.
Bissouma brought down Moises Caicedo for Palmer's first penalty after the Ecuadorian midfielder escaped a red card for a studs-up challenge on Sarr in the first half; VAR official Jarred Gillett deemed that the South American did not use excessive force.
Postecoglou believed that there was a sense of injustice, though, adding: "I think it's kind of where we're at with, the current state of football, where people are just frozen to make big decisions.
"I think referees don't want to make them because they'll go to VAR and VAR doesn't want to intervene, so you're kind of left in no man's land. There's a couple of decisions I thought today that definitely went against us."
Spurs' seventh top-flight loss of the season leaves them languishing in 11th place in the Premier League table, seven points off Manchester City in the final Champions League position, and the Lilywhites return to action away to Rangers in the Europa League on Thursday.
Written by
Ben Knapton