Town fought back from two down to draw 2-2 at West Ham, perfectly setting up Wednesday's Portman Road leg. Two goals in the opening 13 minutes put the Hammers in front but Tommy Miller's freekick just before the break went in off keeper James Walker and Shefki Kuqi equalised in the second period.
The Blues lined-up as expected with Drissa Diallo coming in for David Unsworth whose loan has ended. The Guinean slotted in at right-back with Fabian Wilnis switching to the left. Kevin Horlock came in to add a more defensive outlook to the defence, Darren Currie dropping to the bench.
Town had the ball in the net in the fifth minute, Fabian Wilnis playing in Ian Westlake who finished well but with the linesman's flag already raised.
However, it was the Hammers who would go in front two minutes later. Matthew Etherington appeared to control the ball with his hand as he outpaced Drissa Diallo and crossed low into the box where Marlon Harewood netted from close range, having clearly tripped Richard Naylor as the pair ran in on the ball.
The Town players were incensed by the decision but neither referee Uriah Rennie or his linesman seemed to see the incident.
Darren Bent wasn't too far from putting the Blues back on terms on nine when he found himself beyond the Hammers' defence but the looping ball proved too difficult to bring down and the danger was gone.
Harewood, a former Town loanee in his Forest days, shot wide from 25 yards, Shefki Kuqi doing much the same for the Blues at the other end.
The home side went further ahead in the 13th minute when Etherington again beat Diallo down the left and crossed low. This time Jason De Vos got to the ball but mis-hit his clearance straight to Bobby Zamora, who had no trouble in finding the net.
Sub Matt Richards immediately started to warm-up after the second goal and it looked like an early switch around was on the cards. While Diallo had easily been beaten by Etherington on both goals, the defender had been given little help by Town's once again very narrow midfield.
West Ham had broken well and had taken their chances, but the two-goal lead flattered them. Town had enjoyed a fair amount of possession without creating any opportunities.
Just before the half hour, Darren Bent hit a 25-yard shot which was blocked, and then Bobby Zamora shot a long way wide when well-placed in the area, referee Rennie inexplicably awarding a corner, neither the first nor the last time when Town appeared to be on the wrong end of a consistently inept refereeing performance.
The Blues were starting to have the better of it as half-time approached, Bent striking a 25-yard shot at keeper Walker.
With a minute of the first period remaining, Town were awarded a freekick on the edge of the area, a decision which met with ironic cheers from the more than 6,000 travelling fans, when Tomas Repka fouled Shefki Kuqi. The Czech protested long and hard but succeeded only in winning himself a yellow card and getting the freekick moved to the edge of the area.
Lengthy wall assembling and minor scuffling saw a couple of lectures from referee Rennie, before Tommy Miller hit a low shot which struck Walker's left post, then Walker himself before going over the line.
Strangely the home crowd booed the referee at the break, despite having enjoyed a number of very generous decisions during the half.
Joe Royle decided to make a couple of changes for the second period, Matt Richards coming in at left-back, Fabian Wilnis switching to the right, and Darren Currie taking over on the left of midfield, Ian Westlake replacing Kevin Horlock in the centre.
Zamora again went well wide in the 49th minute, prior to Etherington, a scorer in last season's play-off leg at Upton Park, sending a strike over the bar.
Shefki Kuqi might have got the Blues back on terms with a free header from Jim Magilton's right wing corner, however, the Finn failed to make a full contact and the ball flew well away from goal.
In the 59th minute Fabian Wilnis picked up a yellow card for a foul on Matthew Etherington, a decision the Dutchman felt was harsh.
On the hour Kelvin Davis made a superb save from Anton Ferdinand's header from a cross from the right, pushing the ball into the air and Richard Naylor heading over the bar.
Four minutes later Kuqi made a powerful run down the left before playing the ball inside, Ian Westlake and then Jim Magilton both seeing shots blocked.
Naylor made an important interception in the 76th minute, before Kuqi wasted an opportunity to cross from the left of the area, shooting high and wide from a very tight angle.
Matthew Etherington got his name in the book in the 72nd minute for a wild challenge on Westlake. From the freekick wide on the left, 30 yards out, Darren Currie tried an audacious shot which James Walker did well to push round the post.
Two minutes later the Blues were on terms. Currie sent a deep cross from the left, Bent's effort struck Chris Powell and looped into the six-yard box, Walker and a defender collided and Kuqi stabbed into the roof of the net from close range for his 20th and most important goal of the season.
West Ham sub Mark Noble failed to impress the referee with a rather obvious dive in the area that ought to have warranted a yellow card. Hayden Mullins hit a shot straight at Davis soon after as the home side went looking for the goal that would give them an advantage to take into the second leg.
With five minutes remaining, Richard Naylor received a yellow card for a collision with James Walker, the keeper appearing to kick out at the central defender, Town's man of the match once again.
As time ran down, Harewood shot wide for the Hammers, prior to Currie crossing for Kuqi who headed wide.
Kuqi again went wide in injury time as the Blues finished the stronger of the two sides, with a number of the West Ham players looking shattered by the end.
An excellent draw for Town, leaving them favourites going into Wednesday's home leg. After a difficult first 13 minutes, the Blues, often hindered by poor refereeing fro Uriah Rennie, gradually got on top and were much the better side during the second period.
Joe Royle is likely to stick with the side which finished the game at Portman Road, with Fabian Wilnis much more comfortable at handling Matthew Etherington, the source of most West Ham danger, than Drissa Diallo. Darren Currie added vital width to a Town midfield which had been very lacking in creativity during the first period.
Inevitably memories will go back to the play-offs in 2000 when Town went two goals behind Bolton in the first leg at the Reebok Stadium before a Marcus Stewart-inspired fightback saw them to a 2-2 draw. Could history repeat itself again at Portman Road on Wednesday?
Town: Davis, Diallo (Richards 46), De Vos, Naylor, Wilnis, Magilton, Miller, Westlake, Horlock (Currie 46), Kuqi, Bent. Unused: Price, Bowditch, Couñago.
Attendance: 33,723