The Cobblers are now just one point shy of safety at the foot of League One going into their last four games thanks to a late burst of three goals in 19 minutes at Brisbane Road.
And Gray, who felt they thoroughly deserved the win, now wants his men to secure their safety.
"It was a magnificent win but it would have been a travesty had we not won the game given the chances we had," he said.
"We kept our belief and kept going and we scored three quality goals. We clicked into gear and we got our rewards.
We have to use this result as a springboard now. We have to build on this when we play on Tuesday (against Scunthorpe).
"We can't worry about the results of other teams, we know what we have to do on Tuesday and we have to go and do it."