Town’s FA Cup third round tie at home to Portsmouth remains 0-0 at the break but with the League Two side having had the better of the first half.
Boss Mick McCarthy’s side, which he named publicly on Friday, featured seven changes from the team which drew 0-0 at Burnley last week.
Bartosz Bialkowski was in goal with skipper Luke Chambers at right-back, Jonas Knudsen at left-back and debutant Paul Digby and Piotr Malarczyk - making his first home start - at the centre of the defence.
Cole Skuse was partnered by Luke Hyam in the centre of midfield with Ainsley Maitland-Niles on the right and Tommy Oar on the left. Up front, Brett Pitman started alongside former Pompey frontman Luke Varney.
Freddie Sears and Ryan Fraser were amongst the subs, but there was no place on the bench for Jonny Parr, whose move back to Norway and top flight side Strømsgodset we understand could be confirmed as early as Monday.
Portsmouth included ex-Blues Gary Roberts, who skippered Pompey on his first return to Portman Road, and keeper Brian Murphy.
On-loan Blues defender Matt Clarke was ineligible against his parent club, while former Town academy and reserves striker Caolan Lavery, who is also on loan at Fratton Park, hasn’t been given permission to play in the FA Cup by Sheffield Wednesday.
Pompey created the game’s first chance in the fourth minute when Marc McNulty cut inside Malarczyk on the left of the area, but Digby slid across to block as the on-loan Sheffield United frontman was looking to pick his spot past the advancing Bialkowski.
The Blues created their first opening four minutes later. Digby won the ball and then Skuse sent Oar away on the left but the Australian’s shot was blocked.
Moments later, former Blues keeper Murphy was off his line quickly to claim ahead of Varney from a Maitland-Niles through ball.
Portsmouth were having the better of a lively opening spell playing some impressive passing football and on 11 Knudsen did well to help the ball behind as Adam McGurk looked to reach a left-wing Roberts cross at the far post.
The League Two side should have gone in front in the 17th minute when Ben Davies cut the ball back from the right to an unmarked McGurk, who blazed over when he should have at least have hit the target.
Portsmouth continued to have the better of the game and on 20 Enda Stevens crossed from the left and Roberts headed wide.
Two minutes later, Pompey surrendered possession cheaply midway inside their own half but Pitman failed to find Varney with a pass on the edge of the box. On 24 Varney hit a low shot from just inside the box but Murphy claimed easily.
Pompey threatened again in the 32nd minute when Adam Barton sent McNulty away behind what was now a reshuffled Town backline - Digby had switched to right-back with Chambers moving inside and Malarczyk to the left central role - on the right of the box but Bialkowski was equal to his shot.
Varney shot weakly to Murphy on 35, but the visitors were still on top and Bialkowski was forced into another save in the 40th minute. The ball fell to Kyle Bennett in space on the edge of the box but the Polish keeper got down to his right to save and push away from the danger area.
Pompey squandered another good chance to go in front in the 44th minute when Roberts scuffed well wide from McNulty’s cutback from the right.
Just prior to the half moving into one minute of injury time Skuse was booked for pulling back McNulty.
The whistle was met by muted boos from the home support after a disappointing first half which had been dominated by the League Two side, who but for a couple of poor finishes would have deservedly been in front.
The much-changed Blues line-up looked like a side which hadn’t played together before, while the visitors passed the ball around slickly and dominated possession.
Town only threatened fleetingly on the break, while Pompey created the period’s only serious chances. Half-time changes of personnel from Blues boss McCarthy wouldn’t seem unlikely.
Town: Bialkowski, Chambers (c), Malarczyk, Digby, Knudsen, Skuse, Hyam, Maitland-Niles, Oar, Varney, Pitman. Subs: Gerken, Smith, Fraser, Bru, Tabb, Sears, Kenlock.
Portsmouth: Murphy, Davies, Barton, Webster, Stevens, Hollands, Close; Roberts (c), McNulty, Bennett, McGurk. Subs: Bass, Haunstrup, May, Boco, Tollitt, Evans, Chaplin. Referee: David Coote (Nottinghamshire).