Walsall’s Checkatrade Trophy campaign was ended at the hands of League One rivals Oldham.
Amadou Bakayoko’s 20-yard pile-driver put the Saddlers ahead, but second-half goals from substitute Lee Croft, Cameron Burgess and Lee Erwin booked the Latics’ place in the last 16.
Jon Whitney’s side reverted to a 4-4-2 diamond formation for this Checkatrade Trophy second-round tie.
Craig MacGillivray replaced Neil Etheridge in goal, with Matt Preston, captain for the night, partnering Kevin Toner in the centre of defence.
George Dobson, Isaiah Osbourne, Flo Cuvelier and Liam Kinsella made up the midfield four, while striker Amadou Bakayoko started alongside Simeon Jackson.
Stephen Robinson’s Oldham sprang out of the traps and came within a lick of paint of opening the scoring on six minutes.
Ryan McLaughlin burst into the box and arrowed a powerful right-footed strike towards the far top corner but MacGillivray produced a fantastic finger-tip save to turn the ball onto the bar.
The Latics threatened again, Ollie Banks with a fierce, deflected strike which fizzed narrowly wide following a well-worked training ground free-kick.
Walsall really should have taken the lead from their first opportunity on 18 minutes.
Jason McCarthy galloped forward down the right and fed Bakayoko, who cut ball back for Cuvelier, but with the goal gaping, he blazed wastefully over.
The home side were enjoying a strong spell, with Dobson firing wide from a tight angle after a determined run into the box.
Walsall had a huge let off just past the half-hour mark.
A Cameron Burgess header was brilliantly kept out by MacGillivray at full stretch, with McKay following up to tap home – only for the goal to be disallowed for offside.
Oldham had another opportunity moments later, when Freddie Ladapo found his way past Preston before firing wide of the far post.
The Saddlers ended the half strongly. Cuvelier volleyed wide from the edge of the box, and then dug out a fine cross for Jackson to glance a header wide.
And Walsall went ahead on the stroke of half-time, Bakayoko firing a blistering left-footed drive into the bottom corner from 20 yards for his sixth goal in four Trophy matches.
Half-time: Walsall 1-0 Oldham
Athletic threatened first after the interval, Charles Dunne crossing low for Ladapo who, under pressure from a defender, could only divert the ball over.
The Saddlers fashioned a couple of half-chances to extend their lead, with Jackson dragging wide and substitute Franck Moussa curling over.
Oldham found an equaliser on 69 minutes, as Croft collected possession 25 yards out and drove an accurate low shot into the bottom corner.
And the visitors completed the turnaround four minutes later, when Burgess headed Banks’ pinpoint cross in off the underside of the bar.
Walsall almost levelled straight away, as Scott Laird smashed the ball across the face of goal but a stretching Jackson couldn’t convert from close range.
But the Latics made sure of their progression to round three with a minute of normal time remaining, Erwin checking inside Toner before curling into the bottom corner.
Full-time: Walsall 1-3 Oldham
Team (4-1-2-1-2): MacGillivray; McCarthy, Toner, Preston, Laird; Dobson (Edwards 70’); Cuvelier, Osbourne; Kinsella (Moussa 65’); Bakayoko (Makris 87’), Jackson.
Subs not used: Etheridge, Ginnelly, Sangha, Roberts.
Attendance: 925 (71 Oldham supporters).