Town moved up to third in Division One with a 2-1 win over Derby but were rarely at their fluent best. Darren Bent put the Blues a goal in front in just 30 seconds and a Youl Mawene own goal increased the lead. A strange Marcus Tudgay goal reduced the arrears but Town were rarely in serious danger.
The Blues were forced to make changes at the back with Georges Santos unavailable due to suspension and Fabian Wilnis failing to get over his hamstring injury in time to be involved.
John McGreal came in for his first start of the season with Jermaine Wright reverting to right-back and Tommy Miller coming into the midfield.
Former Town boss George Burley was given a rousing reception by the home fans on his first return to Portman Road as an opposition manager.
Supporters had only just taken to their seats when Richard Naylor sent Darren Bent away behind the Derby defence. Keeper Lee Grant rushed off his line and Bent looped the ball over him and into the net.
It was just the start that Town wanted and the Blues put on some early pressure, Tommy Miller and Bent both shooting straight at Grant.
Derby striker Lee Bradbury had a clear sight of goal from 25 yards in the 10th minute, after Kelvin Davis had kicked poorly. Fortunately for the Blues the on-loan man put his strike wide.
A minute later Adam Bolder had another chance for the visitors but headed Zavagno's cross over the Town bar.
Despite these attempts on goal it was almost all Town in the opening 20 minutes or so, with the Blues winning a succession of corners.
Town were forced into a reshuffle in the 21st minute when Richard Naylor limped off with a hamstring problem, Alan Mahon replacing him.
The Irishman went to left midfield with Chris Bart Williams reverting to centre-half and Ian Westlake slipping into the centre of midfield.
Shefki Kuqi was giving the visiting defence problems and on 23 he sent in a dangerous cross, which a combination of Darren Bent and a defender put wide of goal.
Ian Taylor had Derby's best chances of the period just after the half hour mark. First he shot across the face of Kelvin Davis' goal and then his powerful 30-yard strike flew wide.
Marcus Tudgay made an attempt at a spectacular equaliser with five minutes remaining to the break, overhead kicking a loose ball over the bar.
Just before the break Chris Bart-Williams picked up his ninth booking of the season for dissent.
Prior to the ref's whistle there was just time for Shefki Kuqi to volley high and wide from inside the Derby area, the ball landing in the upper tier of the Greene King Stand.
The half had been a rather scrappy affair and the second period was little different. The first chance came in the 52nd minute, Candido Costa trying to catch Kelvin Davis unawares with a freekick wide on the left, the ball flying into the sidenetting.
Jim Magilton looped the ball on to the roof of the Derby net in the 57th minute before Taylor turned a right-wing cross over the bar from the edge of the Town area.
Shefki Kuqi came close to adding a second for the Blues on the hour but he headed Mahon's deep cross wide.
Kelvin Davis was uncharacteristically loose with his kicking in the 61st minute, the ball crashing against Ian Taylor before dropping out of play.
Mahon, showing flashes of his form from earlier in the season, shot wide from 25 yards on 66, but two minutes later the Blues were further ahead.
Simo Valakari inadvertently played the ball to Darren Bent in a dangerous position in the Rams' half, the striker taking the ball into the area before having his strike saved by Grant.
Sadly for Derby, Youl Mawene was following up and was unable to avoid stabbing the ball into the corner of his own net.
Mawene became a cult hero on the Town terraces, and was called on to shoot whenever he touched the ball with the North Stand keen for the Blues' board to "sign him up”.
Skipper Jim Magilton shot over from 30 yards on 71 and soon after the visitors pulled a goal back, Tudgay appearing to be well offside prior to steering the ball over Kelvin Davis.
Davis was involved in a scuffle with Lee Bradbury soon after, the Town keeper unimpressed with the Portsmouth man for shoving John McGreal into an advertising hoarding. Referee Matt Messias showed both players the yellow card.
Ian Taylor was next into the book for a late challenge on Ian Westlake in the centre circle, Shefki Kuqi following him soon after for protesting about a dubious freekick awarded against Alan Mahon inside the Derby area when the Irishman was in a promising position.
With 11 minutes remaining Darren Bent appeared to be felled on the edge of the Rams' box by Mawene but referee Messias saw no offence.
Tommy Miller put the ball over the bar from a Kuqi knockdown in the 84th minute, and not long after Alan Mahon screwed a shot well wide from the left of the area.
As the game entered injury time Ian Westlake should have added a third but he sent the ball well over with Lee Grant out of position, the goal gaping and Shefki Kuqi screaming for a pass to the edge of the six-yard box.
Town out-battled a Derby side who seldom seriously threatened Kelvin Davis' goal, but the Blues never really hit the heights of last week's performance at Cardiff.
The defensive reorganisation required due to Santos' suspension and the injuries to Wilnis and Naylor could have caused more problems than it did, with McGreal giving a good account of himself and Bart-Williams having little trouble playing the deeper role.
With Sheffield United beaten by Burnley Town are up to third and could find themselves in the automatic promotion positions with victories over Millwall and Norwich City in the next fortnight.
Town: Davis, Wright, Richards, Naylor (Mahon 21), McGreal, Magilton, Bart-Williams, Miller, Westlake, Kuqi, Bent.