Eden Hazard spared Rafa Benitez's blushes when his last-gasp strike crashed into the back of the Sparta Prague net to claim a 1-1 draw which means the Londoners progressed into he last 16 of the Europa Cup 2-1 on aggregate.
The home side went behind to a 17th minute strike from David Lafata, which, had it stood would have taken visitors into extra time.
In truth Chelsea never looked comfortable from the start and with sole striker Fernando
Torres having a stinker of a game, were looking to others to score the necessary goal.
Thankfully for the the brave 38,642 souls that watched the game at Stamford Bridge tonight, that salvation came from the left boot of Hazard.
The opening exchanges were to be expected, with both sides in no mood to concede space. However the Blues had the first chance on four minutes when a fine move on the right saw, Cesar Azpilicueta cut a byline ball back to Fernando Torres. The misfiring striker scuffed a right-footer towards goal, but it faded away harmlessly past Tomas Vaclik in the Sparta goal.
Sparta almost scored on 11 minutes when Vaclav Kadlec ghosted into the far post. His shot was thankfully charged down by Azpilicueta.
Chelsea, already 1-0 from the first leg two weeks ago, missed a sitter on 11 minutes when a brilliant Juan Mata cross was volleyed over the bar by Torres from close range.
Terrible defending, a blight on Chelsea's season, occurred five minutes later.
Just as the Chelsea fans were beginning the obligatory chanting for Roberto Di Matteo, they were instantly silenced as David Lafata popped up from no where to smash the ball home past Petr Cech to level the tie 1-1.
Oscar had a shot charged down as the Blues went in search for the goal to relieve the pressure, while Sparta, clever on the break saw Lafata hit row Z of the Matthew Harding stand.
Cech was forced into a fine save at his left hand post on the half hour as Thomas Prikryl found himself free inside the Chelsea area, and his venomous right-footed effort, on target, brought the best out of the Czech national goalkeeper.
A brilliant save from Vaclik denied Mata on 38 minutes when the mercurial Spain midfielder latched onto a through ball by Oscar and In one swift movement, turned and shot on goal from eight yards out. The goalkeeper reacted instinctively to push the ball over the crossbar and onto the top netting.
Torres missed another effort on the stroke of half-time heading a glancing ball high over the Sparta crossbar.
The Blues started the second half like a house on fire and cut through the Sparta defence immediately after the whistle was blown. Unfortunately, for the home side the ball fell to Ramires who smashed the ball against the Sparta left upright.
On 52 minutes Torres thought his time had come. Racing into a through ball, he had a one-on-one with Vaclik. He tried to chip the out-rushing goalkeeper but failed and Vaclik parried the ball to safety.
John Terry, who stayed up for a free kick on 58 minutes, found himself flicking a back header on goal only to see Vaclik produce an acrobatic save to thwart the Chelsea skipper.
With the Blues pushing forward, they where always susceptible to the counter attack, and on 64 minutes Marek Matejovsky tried his luck from long range having run unfettered for 30 yards. The Sparta skipper looked on in expectation, but his shot inched wide of goal.
Interim boss Rafael Benitez decided a minute later to make his first change, bringing on Eden Hazard for the ineffectual Oscar.
But that changed nothing and the best chance after that fell to Tomas Zapotocny, on 74 minutes, who let fly with a viscous right-footer from just outside the Chelsea penalty area but the ball zipped inches over Cech's crossbar.
Cech needed to be lively three minutes later to smother a close-range shot of Ladislav Krejci as the visitors went for the killer goal.
A Hazard free-kick, on the left went through a melee of players but could not get past Vaclik, who produced yet another fine block.
Azpilicueta almost sealed an 85th minute equaliser, but he saw his long- range effort go just wide of goal.
This was quickly followed by Moses, who flashed a half-volley over the Sparta goal.
Sparta could have won it at the death following a quick breakaway but Kadlec saw his effort to wide.
Then dramatically, the Blues scored.
Substitute Hazard took full responsibility and raced into the Sparta penalty area on the left. He unleashed an almighty left-footed bullet which arrowed past the desperate grasp of Vaclik to crash into the back of the net.
The goal meant the Blues go through int the last 16 of the Europa Cup 2-1 on aggregate.
Teams
Chelsea: Cech, Ramires, Torres, Mata, Oscar, Mikel, Moses, Cahill, Terry, Azilipcueta, Bertrand.
Subs: Turnbull, Cole, Luiz, Hazard, Ferreira, Marin, Benayoun.
Sparta Prague: Vaclik, Svejdik, Přikryl, Matějovský, Lafata, Kadlec, Hybs, Zápotočný, Krejčíi, holek, Vácha.
Subs: Cech, Pamic, Kweuke, Vidicka, Polom, Bednar, Jánoš
Referee : Aleksandar Stavrev