On-loan forward Agyemang is unable to face his parent club for their visit to Fratton Park tomorrow.
That has opened the door to either John Akinde or Ashley Harris for a rare first-team start.
Akinde has been Whittingham’s preferred replacement for Agyemang in recent matches when brought off the bench.
In contrast, Harris has appeared just once in the Blues’ past seven matches – yet he offers something different.
And Whittingham is adamant both are genuine contenders to partner David Connolly tomorrow.
Pompey’s caretaker boss said: ‘I spoke to (Stevenage manager) Graham Westley and his chairman informed him it was a gentleman’s agreement between two clubs that Pat (Agyemang) wouldn’t play so I said “fine”.
‘There has got to be some integrity still left in football. He is their player and we have agreed he will not play.
‘There are no rules, there is nothing in the paperwork saying we cannot play him. That applies to only the Premier League.
‘Pat has done fantastically well for us but it gives someone else a chance to come in and have a game for us.
‘Whoever comes in, and you think about if we keep the same shape, you are looking at Akinde and Harris.
‘It does not necessarily mean that because Pat is seen as a big centre forward that we put John Akinde in there. We will look at Stevenage and their defensive line-up and try to work our way around that to see what is best suited.
‘I don’t see why Harris can’t work with David Connolly.
‘David’s an intelligent player and I would like to think most centre forwards would be able to work with him. He just doesn’t do a target man’s job. He will get himself into positions and Ash is the same.
‘Ash can drop in the hole, or spin in behind so I have no worries over who I pick.
‘It doesn’t have to be a big man-little man. It has worked for us recently but it doesn’t mean we will do the same tomorrow.
‘Akinde is quite aware of the situation with David and Pat playing quite well and has been patient enough to know, if he gets a chance, he will give everything he has got.
‘I probably haven’t seen enough of John playing.
‘But he is certainly somebody who can hold the ball up if it is played into his feet – whereas Ash will move into areas to get the ball into his feet.’
Connolly missed training yesterday with an illness.
However, Whittingham is confident the veteran will be available tomorrow.
He added: ‘Everybody has trained apart from David, who is just feeling the effects of an illness. I am sure he will be all right. I can’t see there being a problem.’