Two places and four points separated the two sides in the regular season table, but now it all comes down to 90 minutes plus possible extra time in match worth at least £170m to the winners - the most lucrative game in football.
Few are old enough to remember the true glory days of Huddersfield Town, when Herbert Chapman led the club to three consecutive First Division titles between 1924 and 1926, becoming the first team in English football history to lift the trophy three times in a row.
The Terriers have not won the top flight since, and more recently have been condemned to a prolonged spell in the lower tiers since their relegation from the First Division in 1972.
Never in the 45 years since have they been so close to returning to the big time, with manager David Wagner - who cut his teeth working alongside Jurgen Klopp at Borussia Dortmund - leading the team to an unexpected promotion charge during his first full season at the helm.
Having finished no higher than 16th in their previous four campaigns in the Championship since their promotion from League One, Huddersfield ended this season fifth and for long spells looked like challenging for automatic promotion.
Table-toppers at stages throughout the campaign, the Terriers won just three of their final 10 games of the regular season to ultimately finish four points below Monday's opponents, but they managed to arrest that form to a certain extent with victory over Yorkshire rivals Sheffield Wednesday in the playoff semi-finals.
Huddersfield needed penalties after 210 minutes of football failed to separate the two sides, but they eventually prevailed in the shootout to become only the fourth club to reach the playoff final in all three divisions.
Only Blackpool have ever won the complete set of playoff finals, but after triumphs in three of their previous four appearances on such a stage, Huddersfield will be confident that they can join that exclusive club.
Wagner's side are unlikely to do it in swashbuckling fashion, though. Twenty-two of Huddersfield's 25 Championship wins this season have been by a single-goal margin and their two most recent playoff final victories - in 2004 and 2012 - came via penalty shootouts after goalless draws.
Indeed, should Huddersfield come out on top on Monday then they will become the first Football League team in history to have won promotion after posting a negative goal difference in the regular season. The Terriers scored just 56 times in the league this season - the lowest tally in the top eight and fewer than 21st-placed Nottingham Forest - while conceding 58.
Helpfully, though, Reading were the only team to concede more goals than Huddersfield in the top seven of the table, while the Royals were also the only fellow playoff contender that Wagner's side beat during the regular campaign.
Recent form: LWLLDW
While Reading cannot point to any First Division titles in their trophy cabinet, they do have much more recent experience of playing in the top flight than Huddersfield and will be hoping that stands them in good stead for the big occasion on Monday.
The Royals are looking to end a four-year exile from the Premier League since their 2013 relegation, and in manager Jaap Stam they have someone with plenty of experience at the highest level - albeit in a playing capacity.
The Dutchman has so far impressed in the dugout too, leading Reading to a third-place finish in his first season in management having previously acted as an assistant in Netherlands.
Like Wagner, Stam arrived at a club that had not previously looked like mounting a promotion charge, finishing 19th and 17th in the two seasons prior to his appointment in June of last year.
Third place this term is the Royals' best finish since they won the division in 2012, but it also brings them face to face with a playoff hoodoo which has plagued them down the years.
Reading have failed to win promotion in each of their previous five appearances in a playoff campaign, including three defeats in finals. Another loss on Monday would see them join Sheffield United as the clubs to have suffered playoff final heartbreak on more occasions than any other.
None of their previous playoff appearances at this level came after a third-place finish in the regular season, though, and victory at Wembley would see them become the 11th team to have won promotion after finishing top of the playoff mini-league.
The Royals will also have the greater momentum behind them having finished the season with seven wins from their final nine games and following that up with a 2-1 aggregate victory over the much-fancied Fulham in the semi-finals.
Reading had been regarded as the outsiders for promotion by the bookies despite their third-place finish, and they will be eager to upset the odds again on Monday.
With four wins from six games against their fellow playoff contenders this season there is form to suggest that they are capable of doing so too.
Recent form: WLWWDW
Stam is also sweating over the fitness of Jordan Obita (ankle) and Garath McCleary (hamstring), both of whom did not start the semi-final second leg against Fulham - although McCleary did feature off the bench.
Huddersfield, meanwhile, have no new injury concerns for the match and manager Wagner could name an unchanged side from the one that beat Wednesday on penalties.
Chelsea loanee Kasey Palmer could be a surprise inclusion in the squad having joined up with his teammates during their warm-weather training camp despite missing the past three months with a hamstring injury.
Huddersfield possible starting lineup:
Ward; Smith, Hefele, Schindler, Lowe; Hogg, Mooy, Kachunga, Brown, Van la Parra; Wells
Reading possible starting lineup:
Al Habsi; Ilori, Moore, Van den Berg; Gunter, Evans, Williams, Swift, McCleary; Kermorgant, Grabban
Head To Head
There has been precious little to separate these two sides since they renewed acquaintances after a 10-year wait back in 2013, with four wins apiece and three draws across all competitions since.
Huddersfield have had the slight edge in Championship meetings, winning four and losing just two of their last eight meetings at this level, but this season both matches ended 1-0 to the home team.
The Terriers won the most recent clash in February courtesy of a Philip Billing goal, but in five meetings since Wagner arrived at Huddersfield there have been two wins each and a draw.
We say: Huddersfield 1-2 Reading (after extra time)
This is a very tough game to call, but whoever comes out on top it is likely to be a tight one. Reading have the greater goalscoring and match-winning ability in their ranks which is why we're siding with them, but Huddersfield could well take it all the way and, having won all five of their previous playoff penalty shootouts, they would then fancy their chances.