Mickleover Sports 3-2 away win at Nantwich Town means Brig are three points from safety with just four games of the season to go.
The visitors took the lead on the half-hour certainly against the run of play.
After a sustained spell of pressure from the home side, Boro broke clear and Ryan Watson converted.
Adam Dodd looked set to equalise soon after but his shot from 10 yards was superbly saved by Thomas Taylor.
The visitors knocked the stuffing out of their hosts four minutes after the interval when Michael Coulson made it 2-0.
Things then went from bad to worse as Callum Spooner was red-carded for a challenge in the centre circle.
Despite the numerical disadvantage, Brig kept going and pulled a goal back from the penalty spot through Alistair Waddecar on 65 minutes.
Unfortunately, the visitors re-established their two-goal cushion shortly three minutes later courtesy of James Walshaw.
Danny Wisdom gave Brig renewed hope two minutes later to make it 3-2, but Walshaw had the final say when he scored again on 77 minutes to make the game safe for the play-off chasers.
Elsewhere, Lancaster City collected their 12th draw of the campaign when they shared the spoils at home with Grantham Town.
Jordan Adebayo-Smith handed the visitors an early lead on three minutes but Charlie Bailey earned a point for the Dolly Blues four minutes from time.
In the NPL West Division, Clitheroe were beaten 2-1 by Prescot Cables at Shawbridge, while Kendal Town were thrashed 5-0 at Chasetown.
In the National League, promotion-chasing AFC Fylde enjoyed a 4-2 victory at home to Eastleigh.
Southport lost 1-0 away at York City in the National League North.