Former Oldham loanee Conor Wilkinson's winner deepened his old club's relegation worries as Walsall came from behind to triumph 2-1 in League Two.
Teenage defender Will Sutton headed Oldham ahead but they remain three points from safety after Emmanuel Osadebe drilled Walsall level and set up Wilkinson to prod home on the volley.
Oldham led after 21 minutes as 19-year-old Sutton - recalled earlier in the day from a loan spell at National League North side Farsley Celtic - glanced home Nicky Adams' corner.
Davis Keillor-Dunn almost added a spectacular second but his chip from just inside Walsall's half drifted narrowly over.
Walsall levelled 12 minutes later as, with Oldham appealing in vain for a foul on a prone Hallam Hope, wing-back Osadebe cut in and lashed a vicious strike into the far bottom corner.
Both sides came close before the break, Christopher Missilou narrowly off target for Oldham, while unmarked Walsall skipper Joss Labadie headed wide from Osadebe's cross.
Carl Rushworth's fingertip save foiled Missilou in a second half of few chances.
But Wilkinson condemned Oldham to a third straight defeat, and left them three points from safety, by diverting home Osadebe's 73rd-minute cross.