The visitors, meanwhile, will be hoping to continue their promising spell of form after taking seven points from their last three matches.
Match preview
Portsmouth may be leading the way in League One, but their promotion push has lost significant momentum following a run of just one win in five league matches.
They looked to have got back on track when they ended a three-game winless league run with a narrow 2-1 victory over Stevenage in their most recent home match.
However, Portsmouth ultimately experienced disappointment in last Saturday's away clash with Cheltenham Town, as they gave up a slender lead to lose 2-1 to the relegation-threatened side.
Although they currently sit two points clear of second-placed Bolton Wanderers, Pompey have played two more games than their promotion rivals, while they are four points better off than Peterborough United and Derby County, who both have a game in hand over the league leaders.
With Portsmouth looking to return to winning ways this weekend, they can take confidence from the fact they have already beaten Leyton Orient on two occasions this season, recording a 4-0 victory in the reverse league meeting before claiming a narrow 2-1 win in November's EFL Trophy clash.
While Pompey were in action last weekend, Leyton Orient have not played since getting the better of Cambridge United on New Year's Day.
Jordan Brown and Dan Agyei both found the net in a three-minute period to guide the O's to a 2-0 away win, ensuring they have now gone three matches without defeat.
Impressively, Richie Wellen's side kept a clean sheet in each of those three matches, which is a significant achievement for a side that conceded in eight straight league games before producing those three strong defensive displays.
Although they face a tough test against the leaders on Saturday, the O's have proven to be a tough team to beat on their travels, having lost just two of their previous 11 away league matches (W4, D5).
However, their recent head-to-head record will be a cause for concern, as the O's have each of their last four competitive meetings since recording a 1-0 win in February 2016.
Portsmouth League One form:
W
D
L
D
W
L
Portsmouth form (all competitions):
L
D
L
D
W
L
Leyton Orient League One form:
L
W
L
W
D
W
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Team News
Portsmouth can no longer call upon midfielder Alex Robertson after the Manchester City loanee was ruled out for the remainder of the season due to a serious hamstring injury.
The hosts are also expected to be without the services of Regan Poole, Conor Ogilvie, Zach Swanson and Tino Anjorin, while Kusini Yengi is away on international duty.
Tom Lowery will provide John Mousinho with an option off the bench after the midfielder returned from a lengthy injury layoff to feature in the matchday squad last weekend.
As for the visitors, Jordan Graham remains sidelined with a long-term injury, while Brandon Cooper has returned to Swansea City following a loan spell.
Forward Ruel Sotiriou is also set to miss a second straight game after being forced off against Wycombe at the end of 2023.
After opening his Leyton Orient account against Cambridge, Agyei is set to retain his up front for Saturday's away trip.
Portsmouth possible starting lineup:
Norris; Rafferty, Raggett, Shaughnessy, Sparkes; Morrell, Pack; Kamara, Whyte, Lane; Bishop
Leyton Orient possible starting lineup:
Brynn; Galbraith, Beckles, Happe, James; Brown, El Mizouni; Forde, Sanders, Archibald; Agyei