Bill Hamid did not make a save in his second shutout of the season for D.C. (5-10-6, 21 points), which is tied with Inter Miami and the Chicago Fire for the final playoff spot in the Eastern Conference pending the result of Miami's match later at FC Dallas.
Columbus (10-5-5, 35 points) continues to struggle and fell into a third-place tie in the East with Orlando City, six points behind second-place Toronto FC with three matches remaining.
The Crew are 1-4-2 in their past seven games.
Gressel gave D.C. a rare lead with his second goal of the season. D.C. has allowed the first goal a league-high 13 times (1-9-3), but the Crew have experienced problems as well, falling behind 1-0 for the fourth straight road game.
D.C. used a combination of passes to stretch the defense, and Yamil Asad had space on the right channel to whip a service to the box.
Gressel lost his markers at the penalty spot and his shot deflected off a Crew player to leave goalkeeper Eloy Room leaning the wrong way on D.C.'s only shot on goal in the game.
The Crew have had two halftime leads in nine true away matches (excluding matches at the MLS is Back Tournament near Orlando, Fla.).
It would have a different score line in the first half if not for a defensive gem by D.C. midfielder Junior Moreno in the 22nd minute when Columbus' Jonathan Mensah headed a corner kick by Pedro Santos.
The ball was directed toward the goal, but Moreno cleared it on one of three shot attempts for the Crew in the half.
Columbus' other good chance came in the 73rd minute on a header by Krisztian Nemeth that went inches over the bar.
On Sunday, the Crew host Philadelphia while D.C. plays at New England.