Wigan were relegated from the Championship after a 1-1 draw at Reading on Saturday, while the race to reach the second tier play-offs is set to go down to the wire.
Wigan defender Charlie Hughes headed home from close-range nine minutes from fulltime to give the bottom of the table Latics hope of staying up.
But third bottom Reading equalised in stoppage-time through Yakou Meite to confirm Wigan's relegation.
Wigan, FA Cup winners in 2013, had been making a late bid to avoid relegation after beating Stoke and Millwall in their previous games.
But they slipped into League One after failing to secure another victory at the SCL Stadium.
Reading, without a win in 12 games, are level on points with fourth bottom Huddersfield, who have three games to play compared to only one for the Royals.
Blackpool were the first team relegated from this season's Championship after their 3-2 home defeat against sixth placed Millwall on Friday.
With third placed Luton and fourth placed Middlesbrough already assured of play-off berths, the battle for the two remaining spots is heating up.
Josh Eccles scored the first goal of his career as Coventry strengthened their grip on fifth place with a 2-0 victory over Birmingham.
Viktor Gyokeres was also on the scoresheet from the penalty spot for Mark Robins' men, who sit three points ahead of seventh placed Sunderland with one game remaining.
Sunderland boss Tony Mowbray suffered a hamstring injury while celebrating a dramatic late equaliser in his team's 2-2 draw against Watford at the Stadium of Light.
Patrick Roberts scored a stunning leveller in stoppage-time that resulted in wild celebrations from Mowbray and his coaching staff.
"I never had a hamstring injury in 18 years as a professional because I was never fast enough but when that goal went in I obviously moved a bit too quick!" Mowbray said.
Watford were two goals ahead thanks to headers from Christian Kabasele in the first half and Ryan Porteous in the 69th minute.
But Luke O'Nien gave Sunderland a lifeline before Roberts' moment of magic left Sunderland two points adrift of Millwall with one game left for each team.
West Bromwich Albion kept their top six hopes alive by coming from behind to beat Norwich 2-1 at The Hawthorns.
Josh Sargent opened the scoring for David Wagner's men in the 41st minute before Conor Townsend's free-kick equaliser before halftime.
Jed Wallace fired in Albion's winner in the 56th minute to leave them two points behind Millwall.
Blackburn, in ninth place, can move level on points with Millwall if they beat Luton in their game in hand on Monday.
Champions Burnley won 2-1 at Bristol City, while Sheffield United, already promoted in second place, thrashed Preston 4-1.