Sunderland were coping with Tottenham's pressure relatively comfortably as the clock ticked towards the hour mark at White Hart Lane.
With the game intriguingly-poised at 1-1, Sam Allardyce attempted to shore up Sunderland's rearguard by bringing on new signing Jan Kirchhoff for his Sunderland debut and switching to five at the back.
But the move back-fired spectacularly, as Sunderland's hopes of building on two back-to-back wins were crushed in the final half-hour.
Up to that point, Sunderland had been well-organised and solid, with Patrick van Aanholt even opening the scoring just before half-time, albeit it was short-lived as Christian Eriksen equalised within two minutes.
The tactical change, plus an absolutely rotten debut from Kirchhoff, simply didn't work though.
Within a minute, Sunderland fell behind to Mousa Dembele's shot, before Eriksen's shot deflected in off Kirchhoff. The German then conceded a penalty, converted by Harry Kane, to give Spurs a decisive 4-1 win.
Jordan Pickford made a confident start to his Premier League debut after an excellent save denied Kane a fifth minute opener.
The England striker curled a low right-footed shot from 25 yards which bounced awkwardly in front of Pickford, but the 21-year-old tipped the ball around the post at full stretch.
Moments later, Dele Alli blasted over the bar from 12 yards out after Sunderland were unable to clear their lines and the ball bobbled around in the penalty area.
But the opening was far more sedate than at Swansea three days earlier, with Sunderland content to sit deep and soak up the hosts' pressure.
Sunderland almost undid all their hard work when the 35th minute when they caught on the break from their own corner after an awful hospital pass from van Aanholt to Jeremain Lens.
As Spurs came forward in numbers, Dembele manoeuvred the ball to Erik Lamela on the left-hand side of the area, but the Argentine's shot across goal was wide of the far post.
But five minutes before half-time, Sunderland went ahead with their first meaningful effort of the game.
Adam Johnson played a wonderful ball inside temporary right-back Alli for van Aanholt to race onto and the left-back brought it under control before beating Hugo Lloris at his near post.
Sunderland's lead lasted less than two minutes though as they were immediately hit by a sucker-punch equaliser.
Pickford produced a smart block to save at the feet of Kane after the striker was freed down the right-hand side of the area.
The ball rebounded to Eriksen, whose scuffed shot bounced towards goal, where Lee Cattermole was unable to clear on the goal-line.
Spurs almost went ahead in first half stoppage time, but Pickford produced another excellent full-length parry to keep out Eriksen's drive from 25 yards.
Sunderland had a chance on the counter-attack in the 53rd minute after Spurs' short-corner routine failed and Jeremain Lens sent it forwards to Adam Johnson and Jermain Defoe on halfway.
Both were the wrong side of the Spurs defence, but didn't have the pace to go through on goal, with Johnson eventually finding Defoe on the left-hand side of the area, who fired into the side netting.
Kirchhoff came on for his Sunderland debut just before the hour, as the Black Cats switched to a 5-3-2 set-up.
But almost immediately, Spurs went ahead when Dembele cut inside off the right wing and hit a low shot from the edge of the box which crept inside the near post.
Spurs then doubled their advantage in the 67th minute when Eriksen hit a hopeful shot from 25 yards which took a wicked deflection off Kirchhoff and looped over the helpless Pickford.
The Sunderland keeper then had to make another smart save to prevent a fifth when he dived high to his right to keep out Kane's angled drive.
Kirchhoff's miserable debut got worse in the 79th minute when he conceded a penalty for a completely needless foul on Danny Rose.
Kane converted the resulting spot-kick, as he smashed it low into the bottom right-hand corner.
Spurs: Lloris, Trippier, Alderweireld, Vertonghen, Rose, Dier, Dembele (Carroll 80), Lamela (Onomah 73), Eriksen, Alli, Kane (Son 87). Subs not used: Vorm, Davies, Wimmer, Chadli.
Sunderland: Pickford, Jones, van Aanholt, O’Shea, Brown, Johnson, Lens (Watmore 76), Cattermole (Rodwell 53), M’Vila, Defoe, Graham (Kirchhoff 59). Subs not used: Borini, Coates, Fletcher, Mannone. Booked: Cattermole (46), Johnson (55)