Middlesbrough look set to hand a debut to on-loan goalkeeper Carl Ikeme.
Ikeme joined Boro from Premier League Wolves on Tuesday following an injury to Jason Steele and will jump straight ahead of Danny Coyne in the pecking order.
Defender Joe Bennett is struggling with a hamstring and will be assessed in the build-up to the clash but midfielder Andy Halliday is doubtful with ankle ligament trouble.
Midfielder Kevin Thomson is a definite absentee as he recovers from ankle and leg surgery and he is not expected to feature until the end of September.
Portsmouth striker Dave Kitson will be handed a late fitness test.
Kitson has been struggling with a thigh injury towards the end of pre-season and is doubtful, meaning Kanu and new signing Luke Varney could start in attack.
Another new face, defender Jason Pearce, will have to wait to make his debut as he is suspended after being sent off playing for Bournemouth last season.
Boss Steve Cotterill has an otherwise fit squad but is still short on numbers despite the arrivals of Varney, Pearce, David Norris and the re-signing of last season's loanee Greg Halford.
Jamie Ashdown should start in goal with Cotterill's fifth summer signing, Stephen Henderson, on the bench.
Israeli defender Tal Ben Haim, who was frozen out last season over a wage dispute, is back in the squad and poised to start at right-back.
