Having topped the table for much of the season, Eastwood’s promotion hopes fall at the final hurdle.
A dip in form and fitness in recent weeks left them vulnerable, and against a red-hot Boston side that had lost just three of their last 24 matches the task was always going to be a tough one – and one made harder by an early red card.
It was a game to forget for Oliver Robinson as he scored an early own-goal before being sent off after 20 minutes.
After the match, a visibly emotional joint manager Martin Ball said: “It’s really hard to sum up how I’m feeling at the moment.
“We led the league for a huge part of the season, came so close to winning it and then had a second chance in the play-offs.
“We thought we had enough to get over the line today, but we started poorly and then went down to 10 men and it’s a long way back from there.
"Ultimately, it’s our own mistakes that have beaten us today, and that’s hard to take.
"It’ll hurt for a long time—there are a lot of devastated lads in the dressing room.”
Boston took an early lead when a dangerous cross from the right was turned into his own net by Robinson under pressure from Harry Limb.
The Red Badgers responded positively, pushing forward with intent but struggling to carve out clear-cut chances.
The game took another turn in the 20th minute as Boston broke away and Robinson brought down an on-rushing forward just outside the box and was shown a straight red card.
Despite the numerical disadvantage, Eastwood came out fighting in the second half.
However, their resurgence was dealt a major blow just after the hour mark.
A long clearance from the Boston goalkeeper saw Limb expertly brought the ball down before seeing his initial shot saved by Sam Wilson.
Unfortunately, the rebound fell kindly, and Limb made no mistake second time around.
Eastwood refused to go quietly and in the 74th minute, their pressure paid off.
A deep cross from Declan Dunn found Aaron Opoku, who rose highest to nod the ball home to give hope, but they could not find a second.