Spalding United left it late to claim their 13th away league win of the season.
Bradley Wells and Conor Higginson scored in the final seven minutes of the derby at Lincoln United on Monday afternoon.
Tulips manager Chris Rawlinson reflected: “Coming away from home to a team who had to win to keep their play-off drive going, we knew they would have a go at us.
“They were in good form having won a lot of games recently so we set a challenge to be solid and go back to what we have done well.
“Eventually, there is a chance you can nick it – that happens in an ideal world!
“I thought the back four, along with Kern Miller when he came on, were excellent in standing up to the challenge.
“The front two could have done better with a couple of chances but they worked so much harder than they did last Saturday.
“We would have taken a scruffy 0-0 draw because it was important not to get beaten again after losing at home to Bedworth United.
“Now we’ve secured third place with 76 points and one game to go.
“We have been in the top three since August which is credit to everyone inside our changing room and those who have moved on during the season.”
We have been in the top three since August which is credit to everyone inside our changing room and those who have moved on during the season.Chris Rawlinson
Midfielder Matt Varley will serve a one-match ban on Saturday at home to Northwich Victoria who suffered relegation on Monday.