Port Vale's hopes of reaching the play-offs were all but ended with defeat at Stevenage, who are in sixth place.
The hosts went close through John Mousinho and Michael Bostwick before Robert Taylor's stinging effort forced a good save from Boro keeper Chris Day.
Lawrie Wilson gave Stevenage the lead when he fired in after Craig Reid's initial shot was blocked.
Vale searched in vain for an equaliser with both Justin Richards and Lee Collins unable to hit the target.
Stevenage manager Graham Westkey told BBC Three Counties Radio:
"They worked hard, they always do as they're a fit bunch of boys.
"They had 10 or 12 minutes before half-time after we'd dominated and that gave them the enthusiasm to keep fighting.
"It meant there was everything to play for going in to the second half."
Port Vale caretaker manager Mark Grew told BBC Radio Stoke:
"We're devastated in there because we've looked quite comfortable and I'm not sure that when we scored it was offside.
"One slip again, somebody making the wrong decision, and we've been punished for it.
"They'll look back at this season and think 'if only'. They'll have big regrets that we haven't got in that top seven."