Nugent and Halford were declared fit at the start of the game in which Pompey started at blistering pace with Utaka getting down the byline and squaring the ball which Nugent could only head into the hands of Neil Sullivan.
Halford then smashed the ball against the crossbar and Doncaster replied with James Hayter having his shot tipped around the post by Ashdown as the visitors began to play their way into the game.
And it was Hayter who scored the opening goal following some atrocious defending from Pompey. Dickinson failed to reach David Healy whose cross evaded two more defenders in blue shirts before falling for the ex-Bournemouth striker who simply couldn't miss.
Sean O'Driscoll's men doubled their lead as the Pompey defence fell asleep after Michael Brown was injured in a challenge, leaving James Coppinger to run through and lob the onrushing Ashdown after being played through by Hayter.
Much frustration followed for the rest of the first half as Pompey struggled to break down resolute Rovers. Kanu was the only player capable of producing a forward pass to a team mate as everyone else seemed clueless. Needless to say, Pompey were booed off at half-time.
Steve Cotterill made changes at the break with Kanu and Sonko making way for Ward, who slotted in a right midfield and Rocha, who partnered Mokoena in the centre of defence.
The result was Pompey dominating the majority of the second half and almost pulled one back when Ward's cross narrowly missed Nugent but arrived to Kitson who forced a save from Sullivan.
Pompey continued to pile on the pressure and finally got some reward when Utaka, who had been a menace down the left side during the second half, got the better of his marker and squared the ball to Ward to poked in from all of one yard out to score his first goal for the club.
And it was thanks to the Nigerian that Pompey drew level as again he got the better of O'Connor and sent a cross into the box which Sullivan couldn't claim, which allowed Nugent to bundle the ball into the net as it bounced fortunately off his back.
From a fans' point of view it looked like that Pompey would go on to win the game, especially as Rocha had a header cleared off the line and Nugent had a goal disallowed for offside.
But football can often throw surprises at you and Healy scored a winner for the visitors ten minutes from time by blasting a powerful shot past Ashdown whose hands couldn't keep the ball out of the net.
Pompey pushed for an equaliser but ended up finishing the game with ten men after Dickinson received a straight red card for a late challenge on Hayter.
Things got out of hand as a little brawl ensued afterwards as Dickinson's frustration boiled over. That frustration was reflected in the stands as Doncaster held on and took three points from Fratton Park.
There isn't too much to analyse following this defeat. We lost to a good team courtesy of a terrible first half performance both up front and at the back.
Carl Dickinson's dismissal may well be a blessing in disguise as he is the weak link in our back four and so Hermann Hreidarsson will finally get his chance to impress next week at Barnsley.
It was also proved in the second half that we play much better football when Rocha is in the side rather than Sonko. I expect Rocha to start next Saturday in Sonko's place which should mean a lot less "hoof" and some more attractive football played that will actually benefit the likes of Nugent and Utaka who can't do much with long balls.
There are positives to take from the second half performance and the main one is that Joel Ward looks like a good Championship player and should Halford not have his loan renewed then Ward is a more-than-adequate replacement.
Utaka also played very well but it'll be good to have Liam Lawrence back in the side next week, as we simply can't rely on our Nigerian players, especially one who can only play a bit-part role in the team, to provide the flair and creativity.
We may have hit a rocky patch in form but there is no need to panic just yet. The chasing pack may have gained some ground on Portsmouth but they're still in a comfortable 14th place - a position that some Pompey fans would gladly accept at the end of the season.
Pompey Player Ratings
Jamie Ashdown: 6 - Good early save but may have done better with the third goal.
Greg Halford: 5 - Won't be missed too much if he returns to Wolves.
Aaron Mokoena: 5 - Struggled.
Ibrahima Sonko: 4 - Rightly hauled off at half-time.
Carl Dickinson: 3 - Red card topped off woeful showing.
David Nugent: 6 - Got the goal his work deserved.
Michael Brown: 5 - Not very effective.
Hayden Mullins: 5 - Didn't see much of the ball.
John Utaka: 7 - Two assists and a constant threat in the second half.
Dave Kitson: 6 - Never stopped working but chances passed him by.
Kanu: 6 - Only creative outlet in the first half.
Ricardo Rocha (Sonko 45): 7 - Team played much better with his arrival.
Joel Ward (Kanu 45): 7 - Grabbed a goal.
Nadir Ciftci (Nugent 90): N/A - No time.