Walsall have suffered two fresh injury blows with Ashley Grimes and Sam Manton ruled out of Saturday's visit of Colchester.
Midfielder Mantom, who had hoped to return from a knee injury against the Us, felt more discomfort during a 4-2 behind-closed-doors friendly win against Wolves.
And Grimes will miss the weekend’s game at the Banks’s Stadium with a calf strain he picked up in last weekend’s defeat at Scunthorpe.
Grimes is expected to be sidelined for around two weeks while Mantom’s return date remains uncertain as he awaits a first appearance of the season.
Boss Dean Smith said: “It’s frustrating and he’s as frustrated as anyone.
“It’s one of those nagging strains that just don’t go away very quickly.
“The good thing is that it is healing, because he was feeling it every time he made a pass and now he’s only feeling it every now and then.
“It’s one of those things we’ve had to be patient with and, as frustrating as it gets, we have been patient.”
Mantom and Grimes have joined James Chambers (hamstring), Jordan Cook (ankle), Ben Purkiss (ankle) and Matt Preston (hamstring) in being sidelined for the weekend while Romaine Sawyers is on international duty with St Kitts and Nevis.
Both the Saddlers and their visitors have yet to win in League One this season and the Us sacked boss Joe Dunne and assistant Mark Kinsella this week.
“It doesn’t matter who we play of what kind of form they’ve got because it’s all about us, how we approach the game and our attitude,” said Smith.
“I have said that to the players because I firmly believe this season it’s a squad of players that can challenge at the top half of the table.
“Whether it’s Colchester or Peterborough, who are top of the league, it doesn’t really matter.
“I was shocked with Joe Dunne and Mark Kinsella going because I thought they’d done a fantastic job in cutting budgets, getting the club on an even keel and promoting the academy and bringing players through.
“But unfortunately that’s football.
“It’s a bit of an unknown now with Tony Humes taking over but the one thing they have is good players – Freddie Sears, Jabo Ibere and Sanchez Watt among others.
“They certainly can’t be taken lightly because they will probably feeling the same as ourselves, that in a few of the games they could have got wins and didn’t.
“It’s a big game for both of us but every game is and it’s one we need to be at our best to win.”