Rafael Benitez's plan to protect his Chelsea stars ahead of the FA Cup tie with Manchester United backfired as the Blues slumped to a 2-1 defeat at struggling Southampton on Saturday.
This was the first of two games in 48 hours for Chelsea and Benitez made seven changes to keep his squad fresh before United's visit to Stamford Bridge for Monday's quarter-final replay.
But first half goals from Southampton's Jay Rodriguez and Rickie Lambert, scored either side of a John Terry equaliser, ensured they will now face United having suffered a major blow in their efforts to secure a top four finish.
Tottenham's victory at Swansea meant Benitez's side slipped back to fourth, just two points ahead of Arsenal who lie fifth.
Meanwhile, Southampton's victory leaves Mauricio Pochettino's side four points above the relegation places.
With a Europa League tie against Rubin Kazan also looming next week, Benitez admitted he would be forced to rotate his squad in an attempt to maintain a challenge on three fronts.
Juan Mata was ruled out because of illness while centre back Gary Cahill is not yet fully recovered from the knee injury that kept him out of England's recent World Cup qualifiers.
Otherwise, the interim manager opted to name Ashley Cole, Ramires, David Luiz, Eden Hazard and Demba Ba among his substitutes, with all five likely to start against United.
Clearly Benitez believes his line-up was strong enough to defeat Pochettino's struggling side and maintain Chelsea's grip on third place.
However, the first half suggested otherwise with Southampton dominating possession and reaching half-time deservedly in front.
The warning signs for Chelsea were there as early as the second minute when Lambert and Rodriguez offered the first glimpse of their threat when they combined to create a shooting chance that Rodriguez fired over.
The opening exchanges highlighted the uncertainty at the heart of the Chelsea defence where Branislav Ivanovic and John Terry looked less than convincing.
Terry in particular appeared uncharacteristically vulnerable as both Southampton strikers found a way past the Chelsea captain to create openings.
Those misses were quickly forgotten though, when Rodriguez made the breakthrough in the 23rd minute after an incisive move.
The former Burnley forward collected a pass from Lambert and exchanged a slick one-two with Steve Davis on the edge of the Chelsea area before placing the ball beyond Petr Cech with an assured right-footed finish.
The lead was no more than Southampton deserved although the shock of conceding did seem to spur Chelsea into action and within 10 minutes the visitors were level.
A Victor Moses chip almost caught out Artur Boruc who tipped the ball away for a corner but the reprieve proved temporary with Marko Marin's corner finding Terry unmarked in front of goal and the defender easily directed his header beyond Boruc.
Relief for Benitez, but it would not last and two minutes later Lambert restored Southampton's lead.
Ryan Bertrand fouled Davis 30 yards out and Lambert curled the resulting free kick up and over the wall and beyond Cech's dive.
Chelsea's response was certainly positive with Moses playing a more prominent role.
The Nigeria international again came close with an attempted chip, saved this time by Kelvin Davis who had appeared as a half time replacement for the injured Boruc.
But with a second goal failing to materialise, Benitez was forced to draw on the replacements he had hoped to keep in reserve until the United game with Hazard and Ramires quickly thrown into the action but had little impact on the course of the game.