Colchester boosted their League Two play-off hopes and damaged opponents Mansfield's aspirations in the process after running out 2-0 winners at home.
Brennan Dickenson and Sammie Szmodics scored as the U's ended a three-match winless run to remain within three points of the top seven and move above the Stags.
Szmodics went close for Colchester early on, while at the other end Mansfield's Matt Green ballooned over a gilt-edged chance from close range.
The U's went ahead in the 20th minute through Dickenson, who raced onto Sean Murray's excellent cross-field pass and beat Stags right-back Hayden White before drilling a low shot in off the far post.
And Szmodics doubled Colchester's lead eight minutes later when he controlled Dickenson's pass in the area and planted a fine shot past goalkeeper Scott Shearer.
Mansfield left-back Malvind Benning dragged a low shot wide of the far post early in the second half and Green squandered an even better opportunity soon after when he scuffed wide, with only keeper Sam Walker to beat.
Benning's deflected effort was cleared from near his own line by Colchester's George Elokobi late on as the Stags were held scoreless for a fourth successive game.