Charlton wrapped up the npower League One title with a 2-1 victory over Wycombe, but the fight for the second automatic promotion spot will go into another week after differing fortunes for the two Sheffield clubs.
The Addicks had already ensured they would be playing Championship football next term, but opened up an unassailable nine-point gap at the top with Saturday's win.
Yann Kermorgant fired Charlton in front after 13 minutes and, although Stuart Beavon replied before half-time, Dale Stephens sealed the points in the 75th minute.
Sheffield United remain second in the table but now sit just one point ahead of city rivals Wednesday following a 1-0 loss at MK Dons.
Alan Smith scored the only goal after 15 minutes, while the Owls snatched a last-gasp victory over Carlisle courtesy of Michail Antonio's strike.
Wednesday went in front through Chris Lines (26), but James Berrett's equaliser eight minutes from time looked to have earned a draw until Antonio's late heroics.
MK Dons are assured of a place in the play-offs along with Huddersfield, who beat Scunthorpe 1-0 with a late goal from Lee Novak.
Stevenage strengthened their play-off hopes with a fortuitous 2-1 victory at home to Brentford.
Clayton Donaldson and Sam Saunders had both missed penalties for the Bees before Craig Reid gave Stevenage a 53rd-minute lead. Luke Freeman added a second nine minutes later with Saunders netting a late reply for the visitors.
Notts County sit two points outside the play-off places with two rounds of fixtures remaining after a 4-2 defeat against Bury.
A Giles Coke own goal brought County level after David Worrall's opener, but a double from Mike Grella opened up a 3-1 lead for Bury.
Mike Edwards reduced arrears once more for the home side and Bury suffered another setback with the dismissal of Andrai Jones, but a last-minute goal from Mark Carrington wrapped up the points.
At the other end of the table, Rochdale's relegation was confirmed with a 2-1 defeat at fellow strugglers Chesterfield.
Goals from Jean-Louis Akpa Akpro (73) and Danny Whitaker (86) sandwiched Scott Boden's 82nd-minute strike to send Dale down.
Exeter live to fight another day after a 4-2 win over 10-man Walsall.
The Saddlers twice led through Alex Nicholls and Florent Cuvelier, with Daniel Nardiello briefly equalising for the Grecians.
But the dismissal of Emmanuele Smith turned things in Exeter's favour, with Alan Gow scoring twice before Liam Sercombe rounded off the result.
Exeter sit five points from safety with two rounds remaining.
Leyton Orient are four points above the relegation zone following a 2-2 draw against Yeovil. Kevin Lisbie gave the home side a 2-0 lead but Andrew Williams and Jonathan Obika secured a point for the Glovers.
Tom Eastman cancelled out Shaun MacDonald's early opener as Colchester shared a 1-1 draw with Bournemouth.
Oldham and Preston played out a 1-1 draw, with Robbie Simpson on target for the Latics and Chris Holroyd replying for North End.
Tranmere were also held 1-1 at home by Hartlepool, with Antony Sweeney earning a point for the visitors after John Walsh's opener.