While the hosts currently sit in 11th place in the League One table, Barnsley occupy sixth position after winning their last two games.
Match preview
After leaving his position as Oxford player-coach to become Portsmouth boss, Mousinho could not have wished for a better start to his managerial career, winning his opening two games.
Unfortunately for the Pompey head coach, his side were unable to secure a third consecutive victory in their away meeting with Peterborough last weekend.
Jonson Clarke-Harris scored a first half brace to give the Posh a two-goal lead, and although an 87th-minute own goal from former Portsmouth player Nathan Thompson halved the deficit, Pompey were unable to avoid their first defeat of Mousinho's reign.
Portsmouth are currently nine points adrift from the top six, but a win over a Barnsley side who occupy the final playoff place would reduce that gap.
The hosts will be confident of picking up at least a point from Saturday's game after avoiding defeat in their previous seven competitive home meetings with the Tykes.
Unlike Saturday's opponents, Barnsley were in action in midweek, claiming a 2-1 away victory over Oxford United.
Bobby Thomas and Nicky Cadden both found the net to give the Tykes a comfortable advantage, before Elliot Moore pulled a goal back for Oxford in the 71st minute, but Michael Duff's side held firm to record a second straight victory.
As a result of Tuesday's narrow win, Barnsley currently have a five-point cushion over the teams sitting just outside the playoff places.
Having lost only two of their last 11 league games, the Tykes head into Saturday's encounter in impressive form, as they attempt to claim a third consecutive victory.
Barnsley have been defensively solid for large parts of the season, especially on their travels, with only two League One teams (Sheffield Wednesday and Derby County) conceding fewer away goals than the 11 Barnsley have let in this season.
Portsmouth League One form:
D
L
L
W
W
L
Portsmouth form (all competitions):
L
L
L
W
W
L
Barnsley League One form:
D
W
L
L
W
W
Barnsley form (all competitions):
W
L
L
L
W
W
Team News
Portsmouth are expected to be without a number of players, with Ronan Curtis, Jay Mingi, Tom Lowery, Joe Rafferty, Jayden Reid and Clark Robertson all sidelined due to injury issues.
Paddy Lane and Di'Shon Bernard joined the club on transfer deadline day, and the new arrivals are expected to feature in the matchday squad, although they are likely to begin the game on the bench.
Joe Morrell missed the defeat to Peterborough through suspension, but he is expected to return to the starting lineup for Saturday's contest.
The visitors are also unable to call upon several individuals due to injuries, including Robbie Cundy, Josh Benson and Luke Thomas.
Matty Wolfe, Aiden Marsh and Slobodan Tedic are also sidelined, while forward Jack Aitchison left the club to join Motherwell on transfer deadline day.
However, Barnsley also made a couple of their own signings on the final day of the window, recruiting Jon Russell and Oli Shaw on permanent deals, and the pair are expected to be on the bench on Saturday.
Portsmouth possible starting lineup:
Macey; Swanson, Raggett, Towler, Ogilvie; Tunnicliffe, Pack, Morrell; Dale, Scarlett, Bishop
Barnsley possible starting lineup:
Collins; Williams, B. Thomas, Andersen, Kitching, Cadden; Phillips, Connell, Kane; Cole, Norwood