Substitute Eden Hazard saved Chelsea's blushes tonight with a stoppage-time strike that saw Rafael Benitez's side sneak into the Europa League last 16 at the expense of Sparta Prague.
Just nine months on from winning the Champions League, the west Londoners only just managed to overcome the side third in the Czech top flight at Stamford Bridge.
Hazard grabbed the all-important goal to avoid extra time and, more pertinently, the potential of an embarrassing Europa League exit on home turf.
Rafael Benitez's side came into the match boasting a 1-0 lead from last week's first leg in the Czech Republic, leading the Spaniard to rest Frank Lampard and Branislav Ivanovic ahead of Sunday's trip to Manchester City.
Any talk of complacency had been downplayed in the build-up but after just 17 minutes the reigning European champions were behind, with David Lafata firing home from close range.
Things could have been different had Fernando Torres found the net with one of the many chances he wasted in the first half, while Juan Mata was denied by a fine save by Tomas Vaclik.
The Sparta Prague goalkeeper's heroics kept Chelsea at bay after the break, having seen Ramires hit the post two minutes into the second period.
The visitors, though, were not being outplayed and looked set to take the tie to extra time - but substitute Hazard had other ideas, lashing home a stoppage-time leveller to put the Blues through on aggregate.
It was a performance that belied Chelsea's confident start to the game.
Victor Moses, one of four changes to the starting line-up in Prague, took just four minutes to create the night's first chance, although his pull-back was directed wide by Torres.
Oscar then saw a hopeful long-range effort deflect behind in a strong Chelsea start, before Torres again came close. This time the £50million striker hooked an excellent Juan Mata cross onto the roof of the net.
Torres was getting a lot of the early action and also headed over, with Vaclav Kadlec producing Sparta's only real threat.
The visitors, though, clearly felt the hosts were susceptible on the break and netted the opener against the run of play.
Kadlec gathered a quick free-kick in the box and jinked past Gary Cahill before laying off for Lafata to rifle home from close range, much to the delight of the 3,000 visiting fans.
Oscar saw a strike blocked as he attempted to immediately hush the raucous visiting support, before Mata poorly curled over a free-kick.
It was the visitors, though, who were in the driving seat, with Petr Cech forced to save a low strike from the unmarked Tomas Prikry.
Marek Matejovsky volleyed over from the resulting corner and, after a break in play for referee Aleksandar Stavrev to receive treatment, Lafata twice tried - and failed with - long-range efforts.
Chelsea looked understandably shell-shocked but ended they first half on top, with only Vaclik's acrobatics denying them a leveller.
Mata met a Ramires ball over the top with a tremendous touch only to see his goalbound strike pushed over by the Sparta goalkeeper.
Torres headed wide unmarked late on, with half-time met by boos from the Chelsea faithful.
Their team returned after the break rejuvenated, with Ramires taking just two minutes to rattle the Sparta goal frame.
The Brazilian hit the near post after latching onto a ball from countryman Oscar, before Moses struck wide from 25 yards.
Torres was the next to threaten but, like so many times already this evening, he could not find the net. The Spaniard raced beyond the Sparta backline but his dinked effort was thwarted by Vaclik.
The Sparta Prague goalkeeper was proving the scourge of Chelsea, with John Terry next to be denied when he tried a flick over his shoulder.
Vaclik palmed that away and Sparta almost capitalised, with captain Matejovsky breaking through the middle only to fire just wide of Cech's far post.
Chelsea fans broke into a chorus of 'Jose Mourinho' soon after as current incumbent Benitez replaced Oscar with Hazard - a change met by boos from the home support.
Chelsea upped the ante in the closing 15 minutes in a bid to avoid extra time, with a Hazard free-kick almost sneaking in, before Azpilicueta and Ramires blazed over.
Kadlec twice came close in stoppage time, before the travelling fans' hearts were broken.
Substitute Hazard was the man who did the damage, finding space in the left-hand side of the box to fire home a stoppage-time leveller and put Chelsea through 2-1 on aggregate.