Steve Howard scored twice to give the Derby the advantage after the first leg of their Championship play-off semi-final at Southampton.
Howard scored a goal in each half for Derby
Saints took the lead when Andrew Surman struck from 20 yards before Howard equalised with a looping header.
Howard then put Derby ahead with a superbly-struck penalty after Pele tugged Stephen Pearson's shirt.
Marek Saganowski twice hit the crossbar for Southampton, while Jon Macken struck the woodwork for Derby.
The match was a superb advert for play-off football, with the contrasting styles making for an engaging encounter.
Southampton played some attractive football and dominated large periods of their first play-off match, while Derby's commitment and sheer force of will ensured they remained a constant threat against a side missing the influential Claus Lundekvam.
The tie started at a breathtaking pace, with a series of crunching tackles setting the tone for a first-half that saw six yellow cards.
Derby keeper Stephen Bywater had to be alert to save a dipping long-range strike from Saganowski after the fit-again forward beat Dean Leacock to the ball and opted to shoot early.
It was a lay-off from Saganowski that Surnam converted with his magnificent left-foot strike after seven minutes as the Rams struggled to come to terms with their opponent's attacking play.
Saints felt they had a strong penalty appeal when Tyrone Mears tangled with Kenwyne Jones as the Southampton striker prepared to shoot but the referee waved play on.
Derby, who struggled to retain possession in the opening half hour, might have equalised from a corner but Stephen Pearson made a poor contact with his header.
But they did restore parity through Howard's superb header after Oakley had hooked the ball back in following a half-cleared corner.
Oakley came close with a shot across goal after a brilliant spin and turn - while at the other end Saganowski opted to hit Djamel Belmadi's telling through ball first time only to be denied by the crossbar.
Jones and Saganowski interchanged passes shortly after the restart, with Bywater saving from the former, while Howard shot narrowly wide from 20 yards for Derby after creating the opening with a clever turn.
And although Saints once again played some flowing football it was Derby who scored next after Pele's rash shirt tug on Pearson saw the Rams awarded a penalty.
Derby boss Billy Davies did not watch as Saints keeper Bartosz Bialkowski got a hand to Howard's spot kick but could not prevent the ball from nestling in the bottom corner.
Macken beaten Pele to the ball and opted to shoot early but, with Bialkowski beaten, saw his effort rebound off the post.
Saints rallied and James McEveley made a brilliant last-ditch block to deny Saganowski, who later struck the crossbar from six yards from Surman's low cross.
But they could not find an equaliser while Gareth Bale, who picked up an injury in the opening half and was substituted shortly after the break, was seen using crutches as he made his way towards a seat late in the game.
Southampton manager George Burley:
"These occasions are never won in the first game and hopefully we can get a result on Tuesday.
"We're very confident that we can turn it round at Pride Park.
"Our away form has been very good all season and we can take positives out of this game. The deficit's only one goal and anything can happen."
Derby manager Billy Davies:
"We won't be complacent as we know it is only half time.
"We came here to put ourselves in contention for the second leg and that's what we've done.
"We showed great discipline and courage to come back - thanks to two great goals from Steve Howard."
Southampton: Bialkowski, Ostlund, Baird, Pele, Bale (Skacel 56), Belmadi, Viafara, Guthrie, Surman, Jones (Best 55), Saganowski (Rasiak 87).
Subs Not Used: Davis, Cranie.
Booked: Pele, Surman.
Goals: Surman 7.
Derby: Bywater, Mears, Moore, Leacock, McEveley, Macken (Teale 77), Oakley, Pearson, Fagan, Howard, Seth Johnson (Nyatanga 90).
Subs Not Used: Camp, Edworthy, Jones.
Booked: Leacock, Pearson, Oakley, Seth Johnson.
Goals: Howard 36, 58 pen.
Ref: M Jones (Cheshire).