While Huddersfield knew that only victory at Ipswich Town and a 15-goal swing would boost their hopes, Birmingham were aware that defeating the Canaries would give them every chance of survival.
However, despite seeing off Norwich by a 1-0 scoreline, Plymouth Argyle earned a 1-0 win over Hull City, and Blackburn Rovers would defeat champions Leicester City by a 2-0 scoreline to dramatically keep themselves in the division.
Sheffield Wednesday also held up their side of the bargain, running out 2-0 victors at Sunderland, to leave Birmingham missing out by a point.
Huddersfield, Birmingham endure frustrating opening 45 minutes
While as many as five teams could have still been relegated at the start of Saturday's action, it was Huddersfield and Birmingham who were always on the brink.
Given the need for a 15-goal swing, Huddersfield's fate was effectively confirmed after Wes Burns put Ipswich ahead in the 27th minute, and Birmingham did not fare much better at St Andrew's.
Requiring all three points to have a chance of survival, Blues barely troubled Norwich City, who knew that a point was enough to earn a playoff spot.
Elsewhere, other results were not going Birmingham's way. Sheffield Wednesday established a 2-0 lead at Sunderland and Plymouth went 1-0 in front against Hull, with Joe Edwards finding the back of the net with a header.
Suddenly, Birmingham's best hope of survival came from Blackburn - managed by former boss John Eustace - losing to Leicester, having remained on level terms up to half time.
Eustace comes back to haunt Birmingham
Birmingham did their bit at the beginning of the second half. After the ball ricocheted perfectly into his path, Paik Seung-ho did the rest with a well-taken header from close range.
However, when Gary Rowett's side required a favour off Leicester City, it did not come, and Blackburn sensationally broke forward to take the lead through Sammie Szmodics.
The division's leading marksman was sent clear down the left flank before being composure personified inside the penalty area as he found the far bottom corner from 10 yards out.
Blackburn's goal effectively left Birmingham relying on Hull to find an equaliser at Plymouth, even if it would mean little for the Tigers' playoff hopes.
With that equaliser failing to come, Plymouth were able to celebrate at Home Park, and Birmingham had to see out the final few minutes of their game with Norwich knowing they would be playing third-tier football for the first time since the 1994-95 campaign.
Szmodics would net his second of the afternoon and 27th strike of an unbelievable campaign from an individual perspective in the 93rd minute to seal Blackburn's 2-0 win and survival - Rovers have ended the season in 19th position in the standings.