Rafael Benitez's Chelsea suffered a lacklustre 1-0 defeat to Steaua Bucharest in their Europa League last-16 first-leg clash in Romania.
In the first of two games in four days and the Blues' 50th game of a turbulent season, last season's Champions League winners went behind after 34 minutes when Ryan Bertrand was penalised for pulling back Raul Rusescu, who converted the spot-kick.
Just like Sunday's opponents Manchester United, Chelsea warmed up for the FA Cup quarter-final with a European defeat, but at least their rivals were defeated by Real Madrid. The result in the Romanian capital will only serve to increase the pressure on interim manager Benitez.
Chelsea began the season in contention for seven trophies and the Europa League is the unexpected eighth after their embarrassing Champions League group stage exit which prompted Benitez's unpopular appointment.
Two chances of silverware remain, but chief executive Ron Gourlay this week insisted a top-four place in the Barclays Premier League and Champions League football next term is the priority.
It is just as well as now they must beat United and overturn a deficit to Steaua in next week's return to keep their trophy hopes alive.
John Terry would not have expected to be playing a key role in the second-tier continental competition this term, but in Bucharest the captain was brought in as one of five changes to the side which beat West Brom.
Due to his recent fitness travails, it must be questionable if the skipper will start at Old Trafford, when the Blues bid to continue their FA Cup defence.
Terry was an unused substitute in Prague in the last round, something which sparked stories of dissatisfaction which were swiftly quashed before dressing room tensions resurfaced.
Steaua, 12 points clear domestically, had shown their ability by overcoming a first-leg deficit to beat Ajax on penalties and Chelsea needed to start better than in the previous round.
An expectant partisan crowd made Benitez feel at home, jeering every time Chelsea had possession as the hosts refused to be intimidated.
Scarcely did they have reason to boo as the hosts enjoyed far superior territory and possession, including three corners in the first 15 minutes and a tame shot wide from the impressive Alexandru Chipciu.
The Blues sat deep and were attempting to play on the counter-attack, with Oscar through the middle, Hazard on the left and Yossi Benayoun on the right behind lone front man Fernando Torres. However, they struggled to string three passes together on a bumpy pitch.
At one point Torres - targeted by a laser pen in the first half - latched on to Petr Cech's long clearance on the right flank, skipped by his marker on the byline, before tackling himself as he prepared to cross to his arriving team-mates.
Chelsea's first corner came after 24 minutes - with Branislav Ivanovic heading Frank Lampard's set-piece wide - and they threatened little in the 10 minutes that followed before going behind.
Left-back Iasmin Latovlevici, earmarked as a dangerman by Benitez on the eve of the match, crossed with the outside of his right foot towards Rusescu, whose attempts to reach the ball were thwarted by a pull from Bertrand.
Referee Sergey Karasev booked the left-back, playing in place of Ashley Cole, and Rusescu sent the resulting spot-kick under Cech.
The Blues were roused into action and had a chance for an equaliser within five minutes following neat interplay between Benayoun and Hazard, but the Israeli's shot was turned around the post by Ciprian Tatarusanu.
The goalkeeper saved a Torres effort on the turn and John Obi Mikel had to be alert to stop Chipciu on the counter, with the Blues exposed.
Time and again the hosts troubled the Blues early in the second period, with David Luiz and Terry forced into some last-ditch interceptions.
A lofted Lampard pass would not drop for Torres in the area, before Juan Mata replaced Benayoun with Chelsea in desperate need of a spark.
Hazard volleyed over after a hopeful Lampard cross fell to him at the back post before the ineffective Belgian was replaced by Marko Marin, the only forward option remaining on the Blues bench.
Tatarusanu saved from Marin after he cut inside on to his right foot and Luiz fired a 30-yard free-kick over soon after.
Terry's brief role as an auxiliary striker ended when he committed a foul challenging the goalkeeper - and he finished the contest on the defensive.