Thomas Tuchel had plenty of food for thought as he watched his first game since formally taking charge of England earlier this week.
The German saw England forwards Dominic Solanke and Anthony Gordon score early goals for their sides, before Alexander Isak scored his 14th league goal of the season to give Newcastle their sixth successive win, fifth in the league.
It was anything but an easy ride for Eddie Howe's men, who needed a highly controversial equaliser and made hard work of beating a heavily depleted Spurs side, who played the second 45 minutes without a central defender.
Tottenham's woes were not helped by a pre-match sickness bug that claimed stand-in keeper Fraser Forster, meaning third-choice goalkeeper Brandon Austin had to make his Spurs debut at the age of 26.
Heung-Min Son and James Maddison were also dropped to the substitute's bench as Postecoglou tried a change of approach, and it looked to have paid off quickly when Spurs took the lead in the fourth minute. Pedro Porro crossed from the right and Solanke worked his way cleverly around Sven Botman to put a diving header in at the near post.
But when your luck is out, little seems to go your way. Spurs thought they had a legitimate claim for handball when Joelinton stopped a Lucas Bergvall pass with his hand, but referee Andrew Madley waved play on, the ball was slipped to Gordon and the England winger drilled it inside the far post. Despite Spurs protests and a VAR check, the offence was deemed accidental and the goal stood.
Spurs were stunned and allowed a rampant Newcastle side to take control. Austin saved well from Gordon, and then Isak shot wide from close range when he should have scored.
But the Swede made amends in the 39th minute when he touched the ball home after Radu Dragusin diverted a Jacob Murphy cross towards goal.
The Romanian failed to reappear for the second half, leaving Tottenham without a recognised centre-back, as Archie Gray and Djed Spence filled in for the second half Dubravka saved well from Pape Matar Sarr before Brennan Johnson clipped the loose ball against a post from a tight angle, and the keeper then dived bravely at the feet of Dejan Kulusevski.
Newcastle were on the backfoot, and started time wasting to break up play, resulting in ten added minutes of stoppage time.
Solanke sent a looping header on to the roof of the net, and then powered another header into the arms of Dubravka as Spurs went searching in vain for an equaliser.
Postecoglou's team have now gone two months without a home win in the league. The manager must be hoping to get more reinforcements in the rest of the month.
Austin 7; Porro 7, Dragusin 5 (Reguilon 46), Gray 7, Spence 6; Kulusevski 7, Sarr 6 (Bissouma 62), Bergvall 7 (Maddison 62); Johnson 6, Solanke 7, Werner 4 (Son 62).
Dubravka 7; Livramento 7, Botman 7 (Kelly 90+2), Burn 7, Hall 6; Guimaraes 7, Tonali 7, Joelinton 6; Murphy 7 (Longstaff 85), Isak 6 (Willock 85) Gordon 7 (Barnes 78)
Andrew Madley 5