The former Pompey boss said the tactic simply didn’t work, with the visitors running out convincing 4-0 winners after holding a slender 1-0 advantage at the break.
Jackett reshuffled his pack during the interval by withdrawing Andy Cannon and Ryan Williams – two key players in recent months – and replacing them with Ben Close and recent arrival Harvey White.
Whittingham believed the move was an attempt to assert greater influence in the attacking third and improve the hosts’ passing game.
But assessing the match afterwards on BBC Solent, the Blues legend said it failed to hurt Grant McCann’s side.
‘He (Jackett) has made the decision, the way this team are playing and the shape they’re playing isn’t causing Hull enough problems, so he wanted to change that,’ said Whittingham.
‘But it didn’t work.
‘It’s one of those things as a manager – sometimes people are frustrated that he doesn’t make enough substitutions and early.
‘This time he did and it backfired on him.’
Asked if it made a difference to the result, Whittingham added: ‘Yes, it did.
‘I think the way Portsmouth went to play in the second half was to try to get Ben Close and Harvey White in more advanced midfield roles, try and pass their way through Hull.
‘But Hull worked hard and sussed that out quite quickly and closed that down, didn’t give Portsmouth any chance to play any passes really.
‘Their work-rate was phenomenal, and physically as well – power in the way they played and the way they broke quick.
‘So, yeah, they really did a job and, given hindsight, I think Kenny Jackett will look back on that decision.’
A message from the Editor, Mark Waldron
The News has launched a new subscription offer which gives you unlimited access to all of our Pompey coverage, starting at less than £1 a week.
You can subscribe here to get the latest news and transfer updates from Fratton Park - and to support our local team of expert Pompey writers.