1. United back in the groove?
Manchester United's opener came as early as five minutes into the contest and allowed them to settle following the crushing disappointment of Tuesday's exit from the Champions League at the hands of Real Madrid.
Further solace arrived when Wayne Rooney doubled the advantage moments later as the sense deepened that this would be a walk in the freezing spring air for United.
Except. The manner of Chelsea's second-half comeback through strikes from Eden Hazard and Ramires spoke of how the Reds had fallen asleep first and become rattled second as their ideas and play became pedestrian.
Beforehand, Sir Alex Ferguson said: "A league and cup double is now our target and if we can pull that off it won't be such a bad season. We will pick ourselves up and give it our best today against Chelsea. It's football and happily we still have plenty to fight for."
They do. But he will want a win when Reading visit on Saturday.
2. Where do Chelsea go from here?
This was a shambolic start by the European champions that for any Blues enthusiast showed a heartening improvement when the sides turned around. Going 2-0 down after only 11 minutes is hardly from chapter one of the cup guide to keeping it tight at an opponent's ground.
This appeared evidence of a squad that while supposedly primed to kick on from last season's glory through a new wave of fresh talent – Eden Hazard, Oscar and Victor Moses – continues to lose the plot.
Before half-time Moses looked to have summed up how far the Roman Abramovich project has fallen when the winger, his side's brightest light thus far, zipped into United's area before taking aim and missed so badly he hit the corner flag.
But the resurgence that came primarily through Hazard's entrance as a second-half substitute means Chelsea can still win two trophies: this one and the Europa League.
3. Nani's disappointment continues
Before kick-off the winger touched upon his and the club's dismay at the events of Tuesday evening when he told the programme: "We're all disappointed, me more than anyone, but we're determined to move on from it and make it a big season. There are many games still to play and still two trophies to go for, so today we focus on the FA Cup."
If the Portuguese thought his personal frustration had gone off the scale after the red card he was issued ended his involvement and turned the Champions League tie, he was about to discover there was a notch or two remaining.
A first half during which he illustrated flashes of the form that got him selected against Madrid after missing a large chunk of the season due to a pulled hamstring ended just before the break when he was replaced by Antonio Valencia due to injury.
4. How shrewd a move was Rafael Benítez's acceptance of the Chelsea role?
The theory ran that the Spaniard would take the Chelsea interim manager's job and no matter how long he lasted in the post would remind the continent's elite clubs of his managerial smarts.
Instead, however culpable the 52-year-old personally was, he entered this quarter-final as the man in charge when Chelsea lost the final of the Fifa World Club Cup, fell away as credible challengers for the championship, and were eliminated from the Capital One Cup by Swansea City. He also had to deal with the fait accompli of Champions League elimination.
When his side went down 2-0 an enfeebled exit from the FA Cup looked to be the next entry on Benítez's Chelsea resume. But the manner of the comeback that keeps the club's hopes of defending the cup alive means the jury remains out on Benítez's decision to succeed Roberto Di Matteo.
5. Javier Hernández
Forget Rooney, the Mexican is surely the unluckiest victim of Robin van Persie's arrival. His clever header that became a lob over the advancing Petr Cech to open the scoring for United after only five minutes was yet another "Little Pea" lesson in the art of finishing.
While he could have had a second when Nani played the 24-year-old in with a flicked attempt that went wide, Hernández's earlier strike was a 16th in 28 appearances for the club so far this term.
This is a ratio that puts him among the band of elite marksmen and from a player who, due to Van Persie's presence, does not benefit from a regular run of starts. Hernández's ill fortune was illustrated after Hazard's fine curling effort pulled one back just before the hour: at this point Ferguson sent for the cavalry in the shape of Van Persie, and Chicharito was forced to trudge off.