The result all-but ended Spurs' chances of a Europa League place (Brighton just need to beat relegated Southampton on Sunday to secure a top-six finish) and even a spot in the much-maligned Europa Conference League is now out of their hands.
They could still finish as low as ninth, proving Antonio Conte's point about how easily the club could slip down the table, though the former head coach is far from blameless for Spurs' shambolic form.
Frankly, the sooner the season ends and Spurs can reset under a new permanent manager, the better for everyone associated with the club.
They still have to go to Sam Allardyce's Leeds on the final day, a daunting prospect after a second-half collapse which suggested Ryan Mason's players are mentally and physically shot.
Harry Kane continues to be a ray of light in the gloom and set yet another record here, becoming the first player to score in 25 different Premier League games in a single season with a magnificent free-kick from 25 yards.
It was his 28th goal of the season, quite a feat given how abject Spurs have been for the duration of the campaign.
The ease with which Brentford turned the game on its head through Bryan Mbeumo's superb double and a late Yoan Wissa strike demonstrated the scale of the job for Spurs next boss, as they predictably cracked under pressure - not for the first time this season.
The priority for the club over the summer should be at least two new defenders and a goalkeeper, as well as perhaps a holding midfield player.
There were, at least, some positives from the first 45 minutes and if the likes of Arne Slot, Luis Enrique or Ruben Amorim were watching, they can take heart that there are some raw ingredients to work with next term.
Despite the absence of Cristian Romero and Pierre-Emile Hojbjerg through injury, acting head coach Mason made a number of bold calls in an attacking 4-2-3-1 system, with Arnaut Danjuma making his first start and Dejan Kulusevski in his preferred role at No.10.
Yves Bissouma made his first start in the League since New Year's Day.
And for 45 minutes, Spurs were bright, the front four interchanging encouragingly and Bissouma adding energy and dynamism to the middle of the park.
Harry Kane with a rocket 🚀
Simply sensational free-kick from the Spurs skipper opens the score! pic.twitter.com/QCuzo2qKd1
— Football on BT Sport (@btsportfootball) May 20, 2023
At 1-0, Emerson Royal had an effort cleared off the line by Rico Henry after a slick move and Danjuma, Kulusevski and Heung-min Son also had chances to extend Spurs' lead.
Spurs were made to rue their missed chances as Brentford stormed back after the interval, Mbeumo making the most of a yard of space to find the far corner and then racing beyond Ben Davies to put the Bees ahead.
Wissa made the game safe after Oliver Skipp lost possession on the edge of his box.
For Thomas Frank, the win was the perfect tonic after the difficult news of Ivan Toney's eight-month ban, offering a reminder that Brentford are well-coached enough to cope without their talisman.
They could still finish above Spurs this term, testament to Frank's remarkable work but damning for the north Londoners.