Ian Baraclough is fearful of Pompey's quality as he bids to banish five-successive defeats.
Scunthorpe find themselves in the bottom three for the first time this season, having failed to pick up a point since November 6.
Now they visit Fratton Park to take on the ever-improving Blues.
And The Iron boss is wary of the challenge ahead as he looks to rally his wilting troops.
Baraclough said: 'It can't be bad when they have someone with the ability of Kanu to be able to bring off the bench.
'Steve Cotterill has gone in there and done a good job.
'I am not sure as a club that they are out of the woods yet but he has galvanised them.
'They still have a few problems but they seem to be a team in a bit of form at the moment.
'After dropping into the bottom three when our game was called off last week, we desperately want to get back into action tomorrow.
'But we know it is going to be a tough game and we are going to have to be prepared to battle.'
On the bigger picture, though, Baraclough knows it's going to be a struggle to haul themselves clear of the relegation zone.
He added: 'It's somewhere we don't want to be and somewhere we want to get out of as quickly as possible.
'We know we let the club down with the way we played at Millwall but the players are itching to put that right.'