The game also provided crucial playing time for Rio Ferdinand and Anderson, who completed 45 and 90 minutes respectively in their ongoing returns from knee injuries. Ferdinand was replaced by Reece Brown at half-time, and the England under-19s defender joined his elder brother Wes in the heart of the United backline.
From the off, Oldham set about their hosts with a vigorous approach. Kirk Millar was narrowly off-target early on, before Jacobsen rattled the Reds' crossbar with a well-taken free-kick from the edge of the area.
Marshalled by Ferdinand and Wes Brown, however, United's defence rarely creaked under the Latics' pressure. Ritchie De Laet, operating as a makeshift right-winger, cleared the bar with the Reds' best opening of a stifling first period.
Just two minutes of the second half had passed, however, when Jacobsen rose to head Andy Crompton's corner past Conor Devlin. Within two minutes United were level, as Ajose fired home an angled shot through a crowd of players.
The quickfire nature of the equaliser sapped Oldham's spirits, and United's dominance grew. Anderson drew a fine save from Latics goalkeeper Josh Ollerenshaw with a long-range effort, but there would be no reprieve for the hosts with 14 minutes remaining.
In possession outside the left-hand side of the Latics' area, the Italian switched the ball onto