Colchester United 0-1 Oldham Athletic
Connor Brown's first goal of the season saw Oldham take a big stride towards safety and deepen Colchester's League One relegation concerns.
The right-back's cross looped off defender Tom Eastman to put the Latics ahead on the stroke of half-time.
The U's wasted first-half chances when Alex Gilbey headed over and Jabo Ibehre nodded into Paul Rachubka's arms.
Dominic Vose curled wide and Ibehre's drive deflected off target as the hosts' second-half luck was also out.
Colchester are now only two points clear of the bottom four with three games left to play, while Oldham move up to 16th, six points ahead of Carlisle in 21st.
Oldham manager Lee Johnson told BBC Radio Manchester:
"It's a big, big win make no mistake. It wasn't pretty, it wasn't sexy football, if you like, but it was vital.
"I thought it was a bit sloppy at times, if I'm being really ultra-critical and honest.
"I thought it was a little bit sloppy in possession and was a tough pitch and a tough occasion to come and play "