Three weeks ago, Chelsea found themselves 2-0 down at halftime at Old Trafford, with every sign from their woeful display suggesting that their already faltering season was about to disintegrate into chaos.
Yet, a combination of an inspirational team-talk from their under-pressure coach Rafa Benitez and the introduction of their star winger Eden Hazard helped spring the side into life. The Blues eventually clawed back from two goals down and probably should have won the game after an impressive comeback.
It was most unexpected, given the Blues' recent form, and it might just have given Chelsea momentum going into the FA Cup Quarterfinal replay.
However, if history tells us anything, it would be that Sir Alex Ferguson does not allow his Manchester United side to get complacent very often, and certainly not twice against the same opposition.
The Red Devils were guilty of taking their foot off the gas in the second half and paid the ultimate price while facing the West London side on their own turf.
The Premier League leaders will be buoyed by their hard-fought 1-0 victory against Sunderland on Saturday, and even more so by Chelsea's 2-1 defeat at the hands of Southampton.
Whether that will give Benitez's men the motivation to bounce back is unknown. But here are five things they can do to avoid falling against Manchester United.