Leeds moved to within a point of the Premier League after scraping past Barnsley 1-0 on Thursday.
A Michael Sollbauer own goal was enough to settle a cagey Championship affair at Elland Road, and while it was far from a vintage Leeds display, it took them a huge step closer to promotion.
They are now five points clear of West Brom, and six ahead of Brentford with two games to go. Marcelo Bielsa's side could also seal promotion before they play again, if either West Brom fail to win at Huddersfield on Friday evening, or Brentford cannot win at Stoke on Saturday.
How can Leeds go up this weekend?
If West Brom fail to win on Friday evening at Huddersfield then their promotion will be confirmed.
If West Brom win, then a failure for Brentford to win at Stoke on Saturday would see them win promotion.
If both sides win, then Leeds will need just a point on Sunday at Derby to guarantee their place in the Premier League.
Should both claim victory, though, then Leeds would still only need a draw at Derby on Sunday to clinch the return to the top flight they have been craving for 16 years.
Barnsley, meanwhile, gave it a real go but a lack of cutting edge saw them fail to claim anything. They remain bottom of the table and four adrift of safety with two games to go.
Leeds edge a tense affair at Elland Road
Barnsley came out with plenty of intent and should have taken the lead on 27 minutes as a Callum Styles corner presented Mads Andersen with a golden opportunity from six yards, but somehow he headed wide.
A minute later, though, in a fashion that typified the Tykes' season, they were behind. Leeds surged immediately up the other end and found Patrick Bamford in behind. His first cross was blocked by Andersen, but his second was turned by Sollbauer into his own net.
Barnsley knew they needed to get something from the game and started the second half with real intensity. Twice they went close in positions where they should have done better, but Conor Chaplin fired wide from the angle, and then Styles put one wide from the edge of the box when he would have been better off playing in a team-mate.
Leeds themselves looked a little more lethargic than usual, but did counter swiftly on 67 minutes to nearly double their lead. Substitute Ezgjan Alioski got down the left and fed Bamford in the box, but Jack Walton pushed his near-post effort wide with his foot.
Barnsley pushed forward and dominated the rest of the game, but could not find a clear-cut chance to really test Leeds. They are now staring a return to League One in the face.
Man of the Match - Patrick Bamford
As a collective Barnsley were the much better side at Elland Road. There was a real lack of quality in both boxes throughout, though, and Bamford's cross that led to the own goal provided the key moment. All promotion charges need ugly wins, and without the striker's work you feel that Leeds would have ended with a draw here.
What the managers said...
Leeds' Marcelo Bielsa: "[Barnsley] fought in a way that deserved something. It is clear we played below our level and didn't get the second goal that would have been good for us.
"The result was open for one goal to make a difference, and we couldn't manage the match in this sense. [It was difficult to play] against an opponent with nothing to lose.
"We will analyse the next match on Sunday and prepare, and take this match as a reference for us. There is no easy match to win. We are going to see what happens [on Friday] and Saturday, but our mind is on Sunday."
Barnsley's Gerhard Struber: "The last few weeks we played very well in every game and have had a good spirit, attitude and created chances. But we can't use our chances at the moment and it's a frustrating and disappointing moment for me and my boys. The mood in the dressing room is down.
"We played very well against Leeds, a big, big opponent, and in the second half we didn't play like a relegated team. This is hard at the moment. It's painful."
Leeds head to Derby on Sunday knowing a point there will be enough to guarantee their return to the Premier League. It could be done before then if West Brom fail to win at Huddersfield on Friday evening, or Brentford fail to win at Stoke on Saturday lunchtime. All three games are live on Sky Sports Football.
Barnsley, meanwhile, will nervously watch all the teams above them play over the weekend before hosting Nottingham Forest on Sunday.