Benjani is battling to be fit for Saturday’s visit of Doncaster.
The veteran striker suffered a hamstring tear during last weekend’s victory over Barnsley.
The problem kept him out of the midweek clash at Ipswich, Dave Kitson taking his place in a two-man strike force.
Now Pompey are sweating on getting him back for the weekend.
But joint-caretaker manager Guy Whittingham is keeping his fingers crossed the former Zimbabwe international can return in time.
He said: ‘Benji has got a slight tear in his hamstring, so we are hoping he will heal quickly.
‘Whether Doncaster is too soon we will have to wait.
‘But we have got our fingers crossed and will be working hard to get him fit.’
So far, Benjani has one goal in nine matches in his second Pompey spell.
Up until his injury against the Tykes, he had started six successive matches.
However, should he return he is likely to find himself behind Luke Varney and Kitson in the pecking order.
The duo have both impressed in the roles during the last two matches.
Meanwhile, Hermann Hreidarsson is closing in on first-team availability.
The Icelandic defender has been troubled by an Achilles problem over the past month.
That has kept him out of the frame for both international and domestic fixtures.
He returned to training at the end of last week and is being eased into the full-time programme.
However, Hreidarsson still faces a battle to break into the match-day squad.
He has not been included in the final 16 since August 13.
That was when he started the shock 1-0 defeat to Barnet in the Carling Cup.