Pompey are sixth in the table with 69 points, but eighth-placed Charlton Athletic, who're just a point worse off, have a game in hand over them.
So it's not in the bag for them yet, while the draw with Accrington Stanley dealt a huge blow to their efforts. The side fought-back from two goals down to lead 3-2, only to concede a third in the fifth minute of extra time from a John Marquis own goal.
In an amazing co-incidence, the Dons are also coming off the back of a pulsating 3-3 draw. Joe Pigott scored in the sixth minute of injury time to force a share of the spoils.
Wimbledon are 19th in the standings, six points off the relegation zone. They haven't confirmed their safety yet, so Mark Robinson's side cannot afford to rest on their laurels.
Wimbledon vs Portsmouth Head-To-Head
In the 28 clashes between the sides, the spoils are equally shared. Both Wimbledon and Portsmouth have won 10 times against each other.
Their first-leg clash this season went Portsmouth's way in a 4-0 victory at home.
Wimbledon Form Guide (all competitions): W-W-W-D-D
Portsmouth Form Guide (all competitions): D-L-L-W-D
Wimbledon vs Portsmouth Team News
Head coach Mark Robinson hasn't reported any injuries ahead of the match. Ethan Chislett and Darnell Johnson are close to a full recovery from their injuries, but are not yet ready to feature.
Winger Ryan Longman is pushing for a start, while Shane McLoughlin might also come into the side.
Doubtful: Ethan Chislett and Darnell Johnson
Jack Whatmough will return from his three-game suspension in a boost for Danny Cowley, who is without any injury concerns at the moment.
That means either Rasmus Nicolaisen or Sean Raggett will have to drop to the bench to make space for Cowley.
Wimbledon vs Portsmouth Predicted XI
Wimbledon (4-4-2): Nikola Tzanev; Luke O'Neill, Will Nightingle, Ben Heneghan, Nesta Guinness-Walker; Ayoub Assal, George Dobson, Alex Woodyard, Jack Rudoni; Ollie Palmer, Joe Pigott.
Portsmouth (4-3-3): Craig MacGillivray; Callum Johnson, James Bolton, Jack Whatmough, Marcus Harness; Tom Naylor, George Byers, Ben Close; Ryan Williams, Ronan Curtis, John Marquis.
Wimbledon vs Portsmouth Prediction
Portsmouth cannot afford any more slip-ups in their playoff endeavors. We expect the visitors to secure a narrow victory over Wimbledon.
Prediction: Wimbledon 1-2 Portsmouth