Derby hope to have stand-in skipper Jason Shackell available.
The defender, an ever-present for the Rams this season following his summer switch from Barnsley, will not train until Friday at the earliest but manager Nigel Clough expects the 28-year-old to be fit.
Shackell limped off after 57 minutes of the 2-0 defeat at Middlesbrough last weekend with a hip problem. He has not trained this week, nor has his central defensive partner Mark O'Brien, who is also expected to recover from a niggle in time.
"We came out of the Middlesbrough game with a few bumps and bruises," said Clough. "Jason will not train until Friday, the same with Mark O'Brien. We are monitoring them both and, hopefully, they will be okay."
Russell Anderson, who missed the trip to the Riverside, trained on Wednesday but the Scottish defender still felt a touch of tightness in his hamstring.
Meanwhile, schoolboy Mason Bennett, who became Derby's youngest ever first-team player when he started against Boro, will again be included in Clough's squad.
Portsmouth will check on Benjani.
The striker missed last weekend's 3-1 win over Doncaster after suffering a minor hamstring tear at Ipswich the previous Tuesday.
If Benjani is passed fit he is likely to be on the bench with Dave Kitson and former Ram Luke Varney set to start in attack after both were on target against Rovers.
Defender Hermann Hreidarsson is the only definite injury absentee with a recurrence of an Achilles problem.
Winger Erik Huseklepp was recalled against Doncaster but the more defensively-minded Joel Ward may be preferred at Pride Park as caretaker bosses Stuart Gray and Guy Whittingham attempt to guide Pompey to a first away win of the season.
