The Rams finished nine points worse off than their opponents at the end of the regular season, yet they are the side in better form heading into this showdown in the East Midlands.
Whereas Leeds have had a couple of weeks to gear themselves up for the playoffs, giving Marcelo Bielsa the luxury of being able to rotate his side slightly, Derby did not nail down sixth place until the final day of the campaign.
A 1-1 draw with Swansea City in their penultimate game left the door open for Middlesbrough and Bristol City to pounce in the final round of matches.
Frank Lampard's side picked up a 3-1 victory over fellow promotion chasers West Bromwich Albion at Pride Park on Sunday, however, to keep them on course for a Premier League return following more than a decade out of the big time.
Derby ended the campaign with just one defeat in their final 12 games - 2-0 to Blackburn Rovers a month ago - and they are the most in-form side of the four playoff contenders over the last six matches.
Finishing sixth does generally mean you are the weakest candidate, though, and that is reflected in the stats. Only Blackpool in 2010 have earned promotion from the Championship having finished in that position over the past 13 seasons.
County certainly have experience of competing in the second-tier playoffs, with this their eighth venture - no team has taken part in more. However, they have won promotion just once in those previous seven seasons (in 2006-07).
Little wonder that Lampard has described his side as "underdogs", then, with history suggesting that the Rams will fall just short.
On form alone, however, three wins in their final four matches offers plenty of promise for Derby. Promotion was always the aim for Lampard this campaign and, given the amount of loanees in his squad, anything less will be considered a huge disappointment.
Recent form in Championship: WDWWDW
A disastrous Easter cost Leeds their big chance of earning automatic promotion. Having spent the majority of the campaign sitting in the top two, United suffered back-to-back losses to Wigan Athletic and Brentford.
That allowed Yorkshire rivals Sheffield United to usurp them and join Norwich City in the Premier League, leaving Leeds to do things the hard way.
Bielsa's side finished the regular season with just one point from their last four games - their worst winless run of the season. To suggest that the wheels have come off would be an understatement, yet it must be remembered that United won 25 matches over the course of the season - five more than semi-final opponents Derby.
Two of those victories came against County - the first time they have achieved this feat in a single season since 2001-02 when both clubs were in the Premier League.
Finishing third has equalled promotion in the second-tier playoffs on 11 previous occasions in its current format - 37% of the time, more than any other position.
Leeds must put their disappointment at missing out on automatic promotion behind them and remember that, ultimately, they are potentially just a couple of wins away from ending their 15-year exile from the Premier League.
Bielsa admits that it is a "dream" of his to guide a team into the top tier of English football, but it remains to be seen whether he can get any more out of his tired players over the next few weeks.
Leeds supporters will also need no reminding that they have never previously won promotion in four previous attempts via the playoffs, most recently losing against Millwall in the League One semi-finals exactly a decade ago.
The Premier League seemed a million miles away back then. Now, 10 years on, it is just three games away.
Recent form in Championship: WWLLDL
Bielsa revealed at his pre-match press conference that centre-half Pontus Jansson is doubtful for the sell-out clash at Pride Park due to an ankle injury.
Forward Tyler Roberts is also sidelined with a similar problem, Barry Douglas and Ezgjan Alioski are long-term absentees and Patrick Bamford is serving the second of a two-match ban. With both left-backs absent, Stuart Dallas will continue to deputise.
Elsewhere, Kemar Roofe has not scored in 11 matches since netting against Derby in January, but he should be given the nod up top on Saturday.
Pablo Hernandez created 116 chances in the Championship during the 2018-19 campaign - 19 more than any other player.
As for the hosts, Lampard was unable to rest any of his key players in the final week of the season, but they have had six days' rest between games.
Tom Lawrence avoided any punishment for simulation in winning a penalty against West Brom so he will retain his place in the forward line this weekend.
Derby possible starting lineup:
Roos; Bogle, Keogh, Tomori, Malone; Mount, Johnson, Holmes; Wilson, Waghorn, Lawrence
Leeds possible starting lineup:
Casilla; Ayling, Cooper, Jansson, Dallas; Hernandez, Klich, Phillips, Roberts, Harrison; Roofe
Head To Head
Leeds won 4-1 at Pride Park early in the season, with Roofe helping himself to a couple of goals. The striker also registered in his side's 2-0 victory in the most recent encounter at Elland Road four months ago.
That clash in January was overshadowed by a 'spy-gate' row when Leeds were fined £200,000 after admitting to sending a member of staff to watch a Derby training session from a nearby field ahead of the match.
Since winning seven successive home games in all competitions against United between May 2007 and December 2014, the Rams have only managed one victory in their last four (D1 L2).
We say: Derby 2-1 Leeds
Leeds collected nine points more than Derby over the course of the 46 regular-season fixtures, yet the Rams finished the campaign a lot stronger and - despite Lampard insisting otherwise - they will be considered slight favourites by many heading into this first leg. Derby have won four home matches in a row, scoring 15 and conceding two, a record they need to make count ahead of Wednesday's return match at Elland Road.