Champions Leicester fell deeper into the Premier League relegation mire as fellow strugglers Swansea took another stride towards survival with a 2-0 win at the Liberty Stadium.
First-half goals from defenders Alfie Mawson and Martin Olsson made it four wins in six league games for the Welsh club, and five defeats in a row for the Foxes.
At the end of a week where the Leicester hierarchy had felt required to publicly back Ranieri, this was not what the Italian needed as his side go ever closer to being the first English champions to be relegated the following seasons since 1938.
They are the first champions to lose five straight games in a season since Chelsea in 1956, are still without a league goal in 2017 and remain a solitary point above the bottom three.
Swansea, meanwhile, are now four points clear of the relegation zone as they continue to build momentum under Paul Clement.
Under the circumstances it was a predictably nervy, cagey opening with both sides fully aware of the opportunity to give themselves some breathing space at the foot of the table.
The visitors survived an early penalty appeal when Gylfi Sigurdsson's strike hit Wes Morgan's hand, but referee Jon Moss waved away the protests.
The hosts were almost immediately forced into an early change as Nathan Dyer - who had been on loan at Leicester during their title-winning campaign - limped off with an ankle problem to be replaced by Wayne Routledge.
Leicester looked to the pace of Riyad Mahrez, Jamie Vardy and Demarai Gray to unsettle Swansea, and Mawson had to be alert to deny the striker after a rapid break from the Foxes.
The centre-half made another telling contribution as he stood up well to block a Mahrez effort after Swansea had given the ball away cheaply in midfield.
It took 34 minutes for either keeper to make a save with Kasper Schmeichel getting down well to repel Routledge's volley from a Sigurdsson flick on, before the Iceland international bent an effort narrowly wide of the post.
There was a bit of niggle about proceedings too, with Leroy Fer and Jack Cork booked for cynical fouls, and Robert Huth getting the same punishment for a clumsy tackle on Tom Carroll.
As the temperature rose, Swansea grabbed the lead. Huth's clearing header only found Federico Fernandez who knocked the ball down for centre-half partner Mawson to volley home his third goal in six games.
Swansea began to find some fluency and they landed a heavy blow in first-half stoppage time by doubling their lead.
Sigurdsson and Fernando Llorente linked up superbly to find Olsson's overlapping run and the Sweden international rifled his first Swansea goal past Schmeichel.
Ranieri sent on Islam Slimani and Ben Chilwell on for Marc Albrighton and Christian Fuchs for the second half and saw his side dominate possession.
But they struggled to create anything of note and when they did manage to send Gray free down the left he could only slice his cross into the grateful grasp of Lukasz Fabianski.
Eventually they did give Fabianski a meaningful save to make as Mahrez slipped in Slimani only for the Pole to rush out and make an important stop.
Swansea dropped ever deeper but Leicester could not summon the guile to make it count as attack after attack foundered against a determined rearguard.
Their day, and perhaps season, was summed up when Vardy - finally afforded a clear view of goal - sliced horribly high and wide.