Chris Dickson scored twice as Cray Wanderers climbed out of the bottom three in the Isthmian Premier on Wednesday night.
It means the worst-case scenario now for Neil Smith's Cray is a play-off place to preserve their step 3 status, as they can no longer finish in the bottom two.
But it also means that East Thurrock need to beat Horsham on Saturday and hope Cray fail to win at Bishop's Stortford. Anything but three points for East Thurrock will leave Cray safe.
Manager Smith was only appointed five games ago but this was his first win in charge of Cray.
"I'm delighted for the club and the boys," said Smith "We came in three weeks ago and Gary (Hillman, chairman) asked us to do our best to stay up and build a club.
"We took the challenge and knew it was going to be a tough one. To be fair we should have got results in the first two games and we shouldn't be relying on the last two.
"We're not done yet, we have got another game on Saturday and who knows what might happen - I really don't know the mathematics of it. I'm delighted for the players, the supporters and the owners of the club.
"It was a must-win. We saw the results from the weekend and we knew we had to win tonight but we didn't want to put the pressure on the boys (by saying that). If we didn't win it's a tough ask to then go and beat Bishop's Stortford."
Experience was key for Cray. Not only did Dickson provide the class in attack but Sam Wood pulled the strings in midfield, talked the youngsters around him through the game - and then scored a wonderful fourth goal late on to wrap up the points.
"Dicko was outstanding, we had a bit of a deeper role for him to help the young guys around him - that's the Dicko I know," said Smith.
"Sam Wood was immense again, he has been outstanding since he came into this club."
After a tense start, Dickson put Cray ahead on 24 minutes, collecting Saul Kader's reverse pass before firing across keeper Arthur Janata into the far corner.
The lead was doubled just five minutes later when skipper Anthony Cook's clearance down the line fell perfectly for Kader, who drove into the box before beating Janata at his near post.
"The first 15 minutes there were a lot of nerves, people making mistakes," said Smith. "We've got a 17-year-old kid in goal and I just hoped my defenders look after him.
"As soon as we got the first goal, you saw the nerves drop and then we got the second one.
"But I've seen so many games here that nothing's over until it's over. I've seen Cray win 4-2 here and draw 4-4."
Cray were in dreamland on the hour when Jamie Yila, having switched to the right, cut inside before firing against the post and the predatory Dickson was on hand to convert the rebound from 10 yards.
East Thurrock got a lifeline with 18 minutes remaining when Tom Barton's robust challenge in midfield went unpunished and the ball fell perfectly for Oli Coker to drill home, via a deflection, from 25 yards.
Cray successfully ran the clock down and added a fourth to settle any lingering doubts four minutes from time. Kader's backheel found Dickson and his flick sent Wood clean through on goal. He slotted beyond Janata with all the poise of a veteran striker.
"That last goal was a brilliant goal - if that was last night, Liverpool scoring it against Manchester United they'd be hoo-ha-ing about it," quipped Smith.
"There was a little backheel, a little flick and Sam Wood goes through and finishes and we're like.....(open mouthed).
"I don't remember doing that at training last night! We had the boys in for training, it wasn't a case of just rocking up after the weekend, we've been working on things in every training session, pattern, shapes and you saw that organisation.
"There's some good players here and they should be better than where they are so I've got to ask the question why are they there (in the table)?
Cray: Boamah, Cook, Kaiser, Hanfrey, Danquay, Aidoo, Smith, Wood (Albon 90mins), Kader (Reid 90mins), Dickson, Yila (Williams 90mins). Subs not used: Brodie, Filip.
East Thurrock: Janata, Wyss, Boswell, Dear, Morrell, Barton, Harry, Spooner, Coker (Dantas-Carvalho 81mins), Miles (Adarkwa 32mins), Ashman. Subs not used: Dutton, Collins, Sartorias.
Referee: Howard Collins.