David Wheeler has been ruled out of Pompey's FA Cup second-round trip to Rochdale on Sunday.
The QPR loanee picked up a back/hamstring injury after coming on as a 74th-minute substitute in the Blues' 2-0 win over Walsall on Tuesday night.
Winger Wheeler has featured 12 times since his summer loan switch from Loftus Road, with only three of them being starts.
And this injury has dealt him another blow as he looks to break into the Kenny Jackett's starting team.
Meanwhile, the FA Cup trip to Rochdale will come too soon for Joe Mason and Dion Donohue.
Mason is still out with a groin injury, while Donohue is thought to be nearing a return following a hamstring injury.
Pompey boss Jackett said: 'David Wheeler picked up a back/hamstring injury on Tuesday night.
'He could be out for a week, maybe two.
'Joe Mason won’t make it either.
‘Neither of those two will be fit, along with Dion Donohue.
‘After that it is the same group and the side that started against Walsall are all fit and available for selection.'