Classy Kevin Cooper climbed off the bench to steer Wimbledon to a 2-1 victory over Portsmouth in the First Division clash at Fratton Park.
The midfielder, subject to a £1m bid by West Ham, struck a 77th-minute equaliser just 12 minutes after entering the fray.
Seven minutes from time, he provided the cross for Republic of Ireland international David Connolly to score the winner.
It was only Connolly's second goal this year but one which has kept alive the Dons' lingering hopes of a play-off place.
Wimbledon's double second-half strike was reward for a stirring display after Leonardo Biagini had given injury-hit Portsmouth a half-time lead.
The Argentinian forward, on loan from Real Mallorca for whom he has figured in the Champions League this season, opened the scoring in the fourth minute.
Biagini settled Portsmouth with his early goal before Graham Rix saw his injury woes worsened when defender Jamie Vincent was replaced by Shaun Cooper in only the 11th minute.
Vincent needed to pass a fitness test in order to take his place in the starting line-up after sustaining a knee injury.
Portsmouth, who were unbeaten in four games, came close to doubling their lead two minutes later when Biagini unleashed a shot from the edge of the box which Kelvin Davis did well to parry.
Beasant was called to make his first save in the 33rd minute when Peter Hawkins fired in a 20-yard effort, after Connolly's original shot was blocked, but the veteran goalkeeper made an orthodox stop.
Wimbledon showed much more urgency after the break and Joel McAnuff saw a snap-shot blocked before his second opportunity flew wide from 25 yards.
Two minutes later Damien Francis nearly got Wimbledon back on level terms but Beasant pulled off a fine save to deny him.
At the other end, Lovell fired over from the edge of the penalty area with Beasant again equal to the task.
However, Beasant was finally beaten when Cooper slotted home after David Waterman had partially cleared Patrick Agyemang's shot.
That was before Connolly netted his second in three games to earn the visitors victory.