Eden Hazard's wonderful stoppage time goal was enough for Chelsea to scrape through to the Europa League last 16 after an aggregate win over a valiant Sparta Prague at Stamford Bridge.
David Lafata's first half goal looked like sending the game into extra time after Tomas Vaclik had brilliantly denied Fernando Torres and substitute Hazard.
The Belgian winger was originally introduced to a chorus of boos by The Blues faithful after replacing Oscar, much to do with their continued disillusion towards manager Rafa Benitez, but he justified the change, rifling home into the roof of the net with merely seconds left on the clock.
The Blues were seeking to avoid the ignominy of exiting two European competitions in one season prior to the last 16 stage, and while Ashley Cole and David Luiz both missed out from the start, Torres, in place of the ineligible Demba Ba and Ramies returned from the win over Brentford.
Sparta made just one change from the defeat in Prague; Josef Husbauer, who impressed immensely in the first leg, making way for Thomas Prikryl.
The hosts looked intent on building on their lead handed to them by virtue of Oscar's goal a week ago, but Torres was guilty of twice spurned the opportunity to double the aggregate advantage, sliding wide after Victor Moses' pull back and then scooping over following Juan Mata's back-post cross.
But Chelsea were made to rue their Spanish striker's misses as early as the 16th minute, a moment set aside by Chelsea fans for their customary tribute to former manager Roberto di Matteo, as Vaclav Kadlec outfought Gary Cahill and crossed for Lafata to smash home.
Marek Matejovsky, the former Reading midfielder, almost doubled Prague's lead on the night, forcing Petr Cech into a save low down to his left as Chelsea threatened to implode in the opening half an hour.
Tomas Vaclik then denied Mata brilliantly after Ramires found him before Torres should have levelled on the brink of the interval but his header flew over the bar, an effort which defined Chelsea's first half plight.
Ramires smashed against the post when he seemed certain to score in the opening moments of the second half, and upon the Brazilian turning provider the onrushing Vaclik blocked from Torres.
The 23 year old Prague stopper was threatening to spoil the European Champions' night as he leapt to stop John Terry's hooked volley.
Sparta's frivolous possession play was handing Benitez's side the onus, but the Czech side's threat remained on the break, Matejovsky capitalising on an error by Terry, but only shooting wide.
Benitez's decision to replace Eden Hazard with Oscar did little to enhance his standing with the home support, but the change almost paid dividends as the former Lille winger's swinging free kick produced a fine save out of Vaclik.
The game looked like slipping into extra time after misses from Ramires and Kadlec, but Hazard popped up in the last minute of stoppage time to save Chelsea's blushes.