Chris Hughton’s men did their bit, beating Wigan Athletic 2-1 at home, and they then watched on as the Terriers conceded a late goal in the evening kick-off which secured Brighton’s top-two place.
If it wasn’t for that late goal, Huddersfield would have been hot on the heels of Newcastle United, who lost 3-1 at Ipswich Town. Instead, they dropped to fourth, after Reading leapfrogged them following a hard-fought victory over Rotherham United.
Sheffield Wednesday and Fulham have been fighting it out for sixth for some time, but they now find themselves both in the top six after respective victories over Queens Park Rangers and Aston Villa. Leeds United dropped to seventh following a home reverse against Wolverhampton Wanderers.
At the other end, Burton Albion won 2-0 at Birmingham City to move above the Blues, and Gianfranco Zola announced his resignation following the loss.
Blackburn Rovers and Bristol City shared the spoils, with Rovers closing the gap on Nottingham Forest after they lost 1-0 at Cardiff City.
Elsewhere, Norwich City defeated Preston North End 3-1, and Barnsley and Brentford played out a 1-1 draw.
Here are the Sky Bet Championship results in full:
Monday 17th April 2017
Barnsley 1-1 Brentford
Birmingham City 0-2 Burton Albion
Blackburn Rovers 1-1 Brentford
Brighton & Hove Albion 2-1 Wigan Athletic
Cardiff City 1-0 Nottingham Forest
Derby County 1-1 Huddersfield Town
Fulham 3-1 Aston Villa
Ipswich Town 3-1 Newcastle United
Leeds United 0-1 Wolverhampton Wanderers
Preston North End 1-3 Norwich City
Queens Park Rangers 1-2 Sheffield Wednesday
Reading 2-1 Rotherham United
Standings: Click here to see the Sky Bet Championship table
Chesterfield were relegated from Sky Bet League One after suffering a 3-1 defeat to Scunthorpe United.
That victory for the Iron moved them up to fourth, overtaking Bradford City who were comprehensively beaten 3-0 by champions Sheffield United in the lunchtime kick-off on Sky Sports.
Fleetwood Town kept up the pressure on Bradford in the race for automatic promotion, defeating Millwall 1-0, but the Lions maintained their spot in the Play-Off places due to Southend United losing to Milton Keynes Dons.
Wins for Bristol Rovers and Rochdale, against struggling Oldham Athletic and relegated Coventry City, kept their slim hopes of a top-six place alive.
At the opposite end, defeats for Port Vale and Swindon Town mean they remain in the bottom four. Shrewsbury Town earned a point at Northampton Town, but remain in trouble, as do Gillingham who lost 3-0 to Charlton Athletic.
The division’s other game produced a goalless stalemate, between AFC Wimbledon and Peterborough United.
Here are the Sky Bet League One results in full:
Monday 17th April 2017
AFC Wimbledon 0-0 Peterborough United
Bristol Rovers 1-0 Oldham Athletic
Charlton Athletic 3-0 Gillingham
Fleetwood Town 1-0 Millwall
Northampton Town 1-1 Shrewsbury Town
Oxford United 2-0 Port Vale
Rochdale 2-0 Coventry City
Scunthorpe United 3-1 Chesterfield
Sheffield United 3-0 Bradford City
Southend United 1-2 Milton Keynes Dons
Walsall 1-0 Swindon Town
Tuesday 18th April 2017
Bolton Wanderers v Bury
Standings: Click here to see the Sky Bet League One table
Plymouth Argyle and Portsmouth secured promotion from Sky Bet League Two with victories on Matchday 43.
Needing just a point to guarantee a top-three place, the Pilgrims hit lowly Newport County for six to end their six-season stay in the division.
Portsmouth had to win at Notts County if they were to join them, and they did, with Jamal Lowe scoring twice late on in a 3-1 triumph.
Pompey also required fourth-placed Luton Town to drop points, and the Hatters could only draw 1-1 at Mansfield Town, one of many teams in the hunt for a Play-Off place.
Three points now separate sixth from 13th, and Blackpool returned to the top seven after a late penalty handed them victory at table-topping Doncaster Rovers.
Carlisle United dropped out of the Play-Off places following a 1-1 draw with Stevenage, while Cambridge United closed the gap after defeating Exeter City.
Wins for Wycombe Wanderers and Accrington Stanley keep them within sight, too, while Colchester United lost ground after sharing the spoils with Morecambe.
At the other end, Leyton Orient secured three vital points at home to Hartlepool United, preserving their EFL status, while Yeovil Town and Cheltenham Town earned important wins to edge them nearer safety.
Here are the Sky Bet League Two results in full:
Monday 17th April 2017
Accrington Stanley 1-0 Crawley Town
Barnet 0-2 Wycombe Wanderers
Cambridge United 1-0 Exeter City
Carlisle United 1-1 Stevenage
Cheltenham Town 2-1 Grimsby Town
Doncaster Rovers 0-1 Blackpool
Leyton Orient 2-1 Hartlepool United
Mansfield Town 1-1 Luton Town
Morecambe 1-1 Colchester United
Notts County 1-3 Portsmouth
Plymouth Argyle 6-1 Newport County
Yeovil Town 3-0 Crewe Alexandra
Standings: Click here to see the Sky Bet League Two table