Sheffield United remain third, while Cardiff are stuck in the relegation zone with three games left of the season to play.
Sheffield United snapped a three-game losing run by beating Cardiff 2-0 to keep their hopes of automatic promotion from the Championship alive.
The win was much-needed for Chris Wilder's side and they managed to get over the line at Bramall Lane thanks to goals from Gustavo Hamer and Ben Brereton Diaz despite not being at their best.
But the gap between Sheffield United and the top two was once again extended to five points by Leeds later on as they won 1-0 at Oxford to reclaim top spot from Burnley on goal difference.
Sheffield United head to Burnley on Monday, live on Sky Sports, likely requiring a win if they wish to avoid falling into the play-offs, having never secured promotion through that route in eight attempts.
The Blades needed some Hamer magic to break the deadlock against Cardiff in an uneventful first half, as he flicked the ball through Cardiff goalkeeper Ethan Horvath's legs with the only shot on target before the break.
Even then, it took a favourable deflection from Tyrese Campbell's strike for the hosts to put Hamer in a scoring position just after half an hour. They needed a similar slice of fortune for the second, too.
The Blades had to wait until the 87th minute before substitute Ben Brereton Diaz put the game beyond doubt, firing in after Kieffer Moore's deflected shot fell to him on the break.
Luck was not on Cardiff's side for either goal, having done well to keep the Blades quiet for much of the game, but they never posed a real threat going the other way.
Omer Riza's side remain in the relegation zone in 23rd, but survival is not out of the question, with a point the difference between Cardiff and safety.
Sheffield United: Cooper, Burrows, Holding (Robinson 85’), Ahmedhodži?, Choudhury, Souza, Peck, Hamer (Seriki 85’), Rak-Sakyi (Brereton Díaz 77’), Campbell (Moore 65’), Brewster (O’Hare 65’). Subs not used: Davies, McCallum, Brooks, Cannon.
Cardiff City: Horvath, Rinomhota, Fish, Chambers, O'Dowda (C), Mannsverk (R Colwill 76’) (Bagan 89'), Robertson (Turnbull 67’), Alves (Willock 46’), Tanner (Ashford 46’), Salech, Méïté. Subs not used: Turner, Goutas, Daland, Šimi?.
