Barcelona face a huge challenge to reach the quarter-finals of the Champions League after losing 4-0 to Paris St Germain in the first leg of their last-16 tie.
Here, we look at some of the more memorable knockout-stage comebacks.
Deportivo La Coruna 4 AC Milan 0 (Deportivo win 5-4 on aggregate) - April 2004
No eyebrows were raised when Serie A giants Milan thumped Deportivo 4-1 in the first leg at San Siro in March, with superstars Kaka, Andriy Shevchenko and Andrea Pirlo living up to their star billing.
But three goals in a remarkable first half at Riazor, sparked by Walter Pandiani's opener, turned the tie around. The Rossoneri were hanging on until the 76th minute, when Fran sent Deportivo through.
Monaco 3 Real Madrid 1 (Monaco progress on away goals after 5-5 aggregate score)
Real Madrid should have read the small print when they sent Fernando Morientes to Monaco on loan in 2003. Annoyingly, he scored against them in the first leg of this quarter-final tie, but they won 4-2.
A healthy lead established, Los Blancos headed for Monte Carlo full of confidence, only for Morientes to once again stick the knife into his employers, with Ludovic Giuly's brace sealing their fate.
Barcelona 4 AC Milan 0 (Barcelona win 4-2 on aggregate) - March 2013
Barca will need to repeat this feat, and then some, if they are to get revenge on PSG. Milan, by 2013 no longer the all-conquering side of old, had scored two unanswered goals in the first leg at San Siro.
Never before had a team recovered from 2-0 down without an away goal, but there was no reckoning with the magic of Lionel Messi, as his brace preceded goals from David Villa and Jordi Alba.
Manchester United 3 Olympiacos 0 (Manchester United win 3-2 on aggregate) - March 2014
Patience with Sir Alex Ferguson's successor David Moyes was already wearing thin among the Old Trafford faithful, and a 2-0 defeat to Greek side Olympiacos a month earlier did little to aid the Scot.
But Robin van Persie gave Moyes a little longer in the hotseat by scoring a hat-trick in Manchester to steer United into the quarter-finals, a stage at which Bayern Munich proved too strong for them.
Chelsea 2 Paris St Germain 0 (Chelsea progress on away goals after 3-3 aggregate score) - April 2014
In the same season Chelsea needed to overcome PSG's 3-1 advantage from the first leg in Paris, where Eden Hazard had grabbed a crucial away goal.
Back at Stamford Bridge, substitute Andre Schurrle gave the Blues hope with a first-half goal but nerves remained frayed until Demba Ba, also off the bench, scored the clincher in the 87th minute.