Town finally confirmed their place in the play-offs via a 1-1 draw with Cardiff. The Blues had to rely on results elsewhere and were helped by Palace's loss at Coventry and West Ham's draw with Wigan. Town now face the Hammers in the two-leg semi-final.
The Blues lined-up as against Sheffield United last week but with Shefki Kuqi taking over from Dean Bowditch up front. Former Blue Gary Croft was in the Cardiff line-up and received boos when he touched the ball in the early stages, although rarely with any enthusiasm. Persistent, if not heavy, rain in the hour before the match left the pitch slippery.
Fans had to make their way to the ground through the vast numbers of police gathered for the game, the security at a level not seen by Town supporters since the Blues visited Moscow to face Torpedo in the UEFA Cup. There was an unprecedented eight police horses on duty, Suffolk Constabulary clearly taking no chances when faced with Cardiff's support.
The visitors started strongly and Kelvin Davis was called into action early on to save a deflected shot from Robert Earnshaw. A minute later the Welsh international was dispossessed in a dangerous position by John McGreal.
Earnshaw's strike partner Alan Lee headed a Gabbidon cross over, then shortly after nodded a Croft cross wide. The visitors were looking the better side and had all the early chances, with Town looking nervous.
Despite this, the Blues went in front in the 26th minute. Matt Richards won the ball from Richard Langley and found Shefki Kuqi in space 25 yards out to the left of goal. Kuqi let fly with a low shot which skimmed off the surface and beat keeper Martyn Margetson to his left.
The Kosovan-Finn celebrated with his usual manner; belly-flopping in front of the Greene King Stand.
The Blues almost went further ahead soon after, Bent playing the ball through to Kuqi who played the ball across the box, the England U21 striker and then Ian Westlake both having efforts blocked.
Kelvin Davis kept Town ahead with an excellent save just before the half hour. The impressive Langley crossed from the right, Lee headed back across goal to Bullock, whose shot was blocked and held by the keeper.
There was a further scare for Town soon after as Cardiff piled on the pressure. John Robinson crossed from the left and Matt Elliott got enough on the ball to deflect it away from the about-to-pounce Robert Earnshaw.
Town continued to look nervous and were rarely at their best, Kuqi's goal having been their only shot until the 37th minute when Jim Magilton's curled freekick gave Margetson little trouble.
The Bluebirds went back on terms in the 40th minute. Tony Vidmar crossed from the left and Lee Bullock's header deflected off Jermaine Wright and into the net.
Portman Road spent the half-time break working out the play-off situation as it stood, with Palace and West Ham behind, Sunderland drawing, Sheffield United winning and Reading losing. The finger calculations showed Town would be sixth if the results stood as they were.
The second half started with the Blues almost scoring a second goal. Jim Magilton's freekick was pushed away by Margetson to his right, John McGreal just failing to get his foot to the rebound.
On 51 Vidmar did well to get in ahead of Kuqi as he tried to get on the end of a Magilton chip. From the resultant corner, John McGreal headed over.
With the Blues still struggling to impose themselves on the game, manager Joe Royle decided that changes were required. Surprisingly, skipper Jim Magilton was switched for Martijn Reuser, while Shefki Kuqi was replaced with Richard Naylor.
Neither substituted player took the decision well, Kuqi kicking a flag before slowly making his way to the dressing room and Magilton throwing the captain's armband down and running off down the tunnel.
Lee headed a Langley corner wide, and then Town had a penalty appeal. Jermaine Wright struck a shot from the left of the area which appeared be blocked by James Collins's hand. Referee Richard Beeby saw the incident as a corner.
Two minutes later, Tommy Miller struggled through a couple of challenges on the 18-yard line but squeezed his shot wide of Margetson's right post.
On 70, Lee hit a cross-shot which went not too far wide. Soon after Earnshaw's effort from a tight angle was saved by Kelvin Davis.
With results elsewhere meaning a point would be enough for Town, the Blues didn't throw men forward in huge numbers, preferring instead to make sure Cardiff couldn't get a goal at the other end.
The only goalmouth activity in the last 10 minutes saw Margetson save Bent's tame effort at one end and Davis did much the same with Langley's 25-yarder at the other.
The final whistle was greeted with a half-cheer, with matches elsewhere still playing. After a couple of minutes, news of the final scores came through and the Blues were confirmed in fifth place, West Ham having notched a late equaliser against Wigan.
By no means a vintage performance from the Blues, a nervy display throughout with Town rarely getting into rhythm. Cardiff hardly looked like a side with nothing to play for and could well be contenders next season.
But the afternoon wasn't really about stylish football, it was simply about getting a result which, although they made heavy weather of it, Town did.
The Blues now face West Ham in the play-off semi-final, the first game at Portman Road on Saturday.
Town: Davis, Wilnis, Richards, Elliott, McGreal, Magilton (Reuser 57), Miller, Wright, Westlake, Kuqi (Naylor 57), Bent.