Sheffield United are one win away from a return to the Premier League after Luton were held 1-1 at relegation-threatened Reading on Wednesday.
A point was enough to realistically secure the Hatters a playoff place as they opened up a 12-point lead on seventh-placed West Brom, who have four games remaining.
But any hope of chasing down the Blades for second place in the Championship faded despite Reading ending the game with 10 men.
Former England striker Andy Carroll put the struggling Royals in front, but was shown a second yellow card for handling the ball into the net as he attempted to double the lead.
An error by home goalkeeper Joe Lumley then ensured Reading remain in the bottom three as Carlton Morris headed in an equaliser nine minutes from time.
But a draw leaves Luton still seven points behind Sheffield United with just three games remaining.
Middlesbrough moved a point behind Luton in fourth with a 3-1 win over Hull as Chuba Akpom became the first player to score in nine consecutive Championship home games.
Akpom completed a second-half turnaround with his 29th goal of the season after Hayden Hackney and Cameron Archer had responded to Allahyar Sayyadmanesh's opener for the Tigers.
The drama of the night came at Ewood Park as Coventry goalkeeper Ben Wilson scored a 95th-minute equaliser to snatch a 1-1 draw at playoff rivals Blackburn.
"I thought yeah we've got to do it because it might just cause a little bit of mayhem and it did," said Coventry boss Mark Robins on the decision to send Wilson forward.
"Credit to Ben, being in the position he did. He actually went between the sticks, went in where the striker should be and he's ended up getting a goal."
A point keeps Coventry just one point behind sixth-placed Rovers.
At the other end of the table, Cardiff boosted their survival hopes with a 3-1 win at Watford.
Sory Kaba scored a stunning overhead kick as all the goals came before halftime at Vicarage Road.
QPR are just one point outside the relegation zone after a 1-1 draw with Norwich, which did little for the Canaries hopes of climbing into the playoffs.
Preston's chances of a top-six finish were also dealt a blow as they were beaten 4-2 in a bad-tempered clash at Swansea.
A mass touchline brawl saw Preston boss Ryan Lowe and former Wales international Joe Allen - who had been substituted - sent off five minutes from time.
Joel Piroe scored twice for the Swans to leave Preston still two points adrift of the playoff places in 11th.