Pompey could leapfrog Peterborough United with a win against Doncaster Rovers today.
But defeat to Donny could see the Blues drop to 11th in the League One table.
If Kenny Jackett’s men get three points at Fratton Park they could be two points off the play-off positions, if results go their way.
Rotherham currently sit sixth on 47 points and host AFC Wimbledon at the New York Stadium.
Charlton (46 points) and Peterborough (43 points) are the other sides between Pompey and the play-off spots.
The Posh welcome Southend to London Road, with Chris Powell now in charge of the Shrimpers.
In the reverse fixture, the two sides shared the points in a 1-1 draw in October.
Charlton face Oxford United at The Valley and are in good form after winning their past three league outings.
A loss to Darren Ferguson’s side would could see a drop down League One continue.
Gillingham will look to continue their impressive form as they go to leaders Wigan.
The Gills currently sit in 10th place on 40 points after four wins on the bounce.
Steve Lovell’s side are also unbeaten in their last eight league games, winning six of them.
If 11th-placed Bristol Rovers beat Shrewsbury on Saturday, they could go level on points with Pompey.
There’d need to be a five-goal swing, though, for the Pirates to move above Jackett’s side on goal difference.
Only six points separate Pompey in ninth and 15th-placed Fleetwood Town in a congested table.
Plymouth, in 13th, have lost just one of their past 10 league games - but entertain second-placed Blackburn.