Ryan Broom's 90th-minute equaliser denied Gillingham all three points in a 1-1 draw against Burton.
The Gills knew they had to win both of their remaining games to stand a chance of making the play-offs but Portsmouth's win at AFC Wimbledon took it out of their hands despite them dropping two points at the Pirelli Stadium.
Jordan Graham grabbed the opening goal of the game, nipping in to capitalise on an error in the Burton defence and rounding keeper Kieran O'Hara for his 13th goal of the season eight minutes from half-time.
Vadaine Oliver twice went close for the Gills in the second half, firing wide at the near post and just failing to get his head to a teasing cross from Alex MacDonald.
But Burton substitute Broom had the last say, finding the bottom corner of the net from the edge of the box at the second attempt after a scramble in the Gills box to ensure that Albion salvaged a hard-earned point.