Enfield Town were beaten 5-3 by East Thurrock United on Monday and the relegation battle will now go down to the final day.
The defeat was particularly damaging for Enfield, with Thurrock just a place and two points behind them in Ryman Premier standings.
George Borg's side got off to the ideal start when Ryan Doyle thundered home his first goal for the club after just two minutes.
Just five minutes later Mitchell Gilbey equalised for Thurrock following a defensive lapse.
East Thurrock then took the lead when Steve Sheeham put stand-in goalkeeper Ryan Chalk under pressure from a high ball and bundled home.
After 19 minutes it was 3-1 when the unfortunate Chalk fumbled a Gilbey shot into his own net.
It was 4-1 before half-time when Neil Richmond took advantage of slack marking from a free-kick to net.
With Raheem Sterling-Parker and Michael Ewang thrown on at half-time, Enfield got one back when Mitch Hahn netted a header.
The fight-back was shortlived, Lewis Smith burying after Chalk had saved a Sam Higgins penalty.
Liam Hope got his 101st Enfield goal in the final minute, but it was too late for Town to mount a comeback.
The Towners had drawn 1-1 against Wingate and Finchley on Saturday, despite losing goalkeeper Noel Imber to injury.
Imber was stretchered off with a dislocated shoulder and replaced between the sticks by centre half Lee White, who made a blinding, point-blank save towards the end of the game to keep the score at 1-1.
Hahn put Enfield ahead before Josh Kennet equalised for Wingate and Finchley.
Enfield could have escaped with a win when Mark Kirby struck the crossbar with an effort off his shoulder.
Finchley finished with ten men after Marc Weatherstone was sent off for two bookable offences