Leicester's play-off hopes were dealt another major blow as they suffered a third straight league defeat at Barnsley, going down 2-0.
Nigel Pearson's side have slipped from second to seventh having failed to win in March and just once in their last 10 outings.
However, Barnsley, who started the afternoon in the bottom three after Saturday's defeat to fellow strugglers Sheffield Wednesday, did not look like a side fighting the threat of relegation as they made it a hat-trick of wins at Oakwell and could even afford a missed penalty.
A Michael Keane own goal and a strike from on-loan striker Chris O'Grady, before Jason Scotland missed from the spot, were enough for the Tykes to record only their second home league win against Nigel Pearson's side in over 20 years.
The inclusion of O'Grady, who was ineligible to play against his parent club at the weekend, was one of three changes made by manager David Flitcroft, who also recalled midfielder Stephen Dawson and veteran forward Scotland.
The Foxes made made three changes to the side that was beaten by Millwall at the weekend, including a first start of the year for centre-back Zak Whitbread in place of the suspended Wes Morgan.
The hosts got off to a flying start when full-back Scott Wiseman surged past two blue shirts before delivering a fizzing cross which was turned into his own net by the unfortunate Keane after just four minutes.
Scotland looked to have doubled the advantage moments later when he turned in O'Grady's low ball but the referee's assistant had already raised his flag.
Pearson's side had no response for the rampant Reds who twice went close with further efforts from Jacob Mellis and Martin Cranie.
'We want our money back' was the message from the away supporters as they jeered their team for the duration of a dismal performance.
Those demands grew louder shortly after as Dawson, on his return from injury, narrowly found the wrong side of the post with a delightful lob over Kasper Schmeichel after breaking the offside trap.
The instrumental O'Grady made no mistakes five minutes before the break though when he steered a cool finish beyond the Foxes skipper following a neat interchange with Scotland.
Fears that the hosts may become complacent after the restart were soon quelled when Paul Konchesky rather clumsily fouled David Perkins inside the penalty area.
Scotland stepped up to take it but his strike did not befit his lengthy run up as he rolled a tame effort down the middle and into the feet of Schmeichel, who steered it away.
There was still no sign of a response from the visitors and Perkins had already turned to celebrate a third goal after a melee in the box only to see the flag raised for the second time.
Blues substitute Jeffrey Schlupp was next to question Andy D'Urso and his officials after his strike was ruled out for offside, completing a treble of disallowed goals.
Former England striker David Nugent finally introduced himself to the action with just over 10 minutes remaining but could not beat Luke Steele with a towering header.
Steele's handling was not so assured moments later as he fumbled a looping ball against his own crossbar before recovering well to block Schlupp's effort on the line.
The visitors piled forward in the final stages but found no way past Steele and his dogged defence as Flitcroft's men survived a late onslaught to climb back out of the drop zone at the first attempt.