The unbeaten record is all over for Spalding United’s under-21s.
Another victory on Tuesday night would have secured the south section championship and booked a spot in next month’s grand final.
Instead, they will need to win the final league game against Harrowby United at the Sir Halley Stewart Field on Thursday.
Marcel Chipamaunga’s second-half equaliser – after only three minutes on the pitch – looked set to earn a point and maybe even lead to a late winner.
But ex-Spalding striker Gregg Smith’s second goal sealed the ‘home’ success for Boston United on the 3G pitch at Carre’s Grammar School in Sleaford.
Scott Floyd, Jordan Neil and George Stainfield went close to breaking the deadlock.
However, at the other end, Spalding failed to clear Jamie Gaukroger’s corner and the ball broke for Smith to fire home via a deflection.
Daniel Moulds missed a free header from Neil’s corner but Chipamaunga’s arrival made a huge impact.
He raced clear and found the bottom corner of the net before two saves from Seth Greeves.
Neil was also denied and Hayden Havard fired wide against his former club.
Stand-in skipper Alex Smith was beaten by a chip from the right of the penalty box into the far corner.
Smith nodded wide Jordan Tate’s free-kick when he should have completed the hat-trick.
Jonny Lockie wasted an even better chance inside the six-yard box when he somehow knocked the ball too high.
Floyd’s effort was flicked behind to safety and there was no way back, even at the end of stoppage-time when keeper Smith came forward for Neil’s corner.
The Tulips’ performance before the break meant they could have no complaints – but the unbeaten record had seemed safe for a brief spell until Smith struck again.
4-2-3-1: Greeves; Gaukroger (sub Ball 70 mins), Rodger, Gray, Brown; Evison, Tate; Bark, Young, Pratt (sub Jackson 60 mins); Smith. Subs not used: Swaby, Holland.
5-3-2: Smith; Gordon, Christopher, Moulds, Moyses, Neil; Havard, Floyd, Stainfield; Couzens (sub Chipamaunga 60 mins), Lockie. Subs not used: Maria, Buckley, Heeley, Britton.
Smith (38 mins, 1-0); Chipamaunga (63 mins, 1-1); Smith (77 mins, 2-1).
Jordan Neil – always looking to get forward in wing-back role, forced a couple of saves and set-pieces also posed problems.
Harrowby United (H) – Thursday.