Only two weeks ago runaway Premier League leaders Liverpool had lost just twice in 41 matches in all competitions this season.
Fast forward 14 days and Jurgen Klopp’s Reds have surrendered their rampant form, with defeat at Atletico Madrid, a 3-0 humbling at Watford and now this hefty blow in west London.
Liverpool still boast a 22-point Premier League lead over second-placed Manchester City, with a first top-flight title in 30 years no doubt a mere formality.
But there can be no doubt either that the exacting Klopp will be fuming with this faltering form.
Chelsea emerged worthy winners to storm into the quarter-finals but were left to count an ever-increasing injury toll, with Mateo Kovacic and Willian the latest Stamford Bridge stars to pull up with problems.
Manager Lampard will be boosted enormously, though, by a virtuoso turn from 18-year-old Scottish midfielder Billy Gilmour.
The teen sensation more than merited his inclusion in a performance of poise and maturity, digging out his defence as often as threading killer passes.
Chelsea could now face Everton in Sunday’s Premier League clash at Stamford Bridge missing as many as nine frontline stars.
The Blues’ midfield could be stretched to the limit, with N’Golo Kante nursing an adductor problem and Ruben Loftus-Cheek a long shot to start as he seeks match fitness after Achilles surgery back in May, while Jorginho is suspended.
Chelsea battled their way to a 1-0 lead at half-time, with the resurgent Kepa keeping the Blues afloat.
The recalled Spain stopper denied Mane early on before the Senegal striker failed to connect with Divock Origi’s cross.
Kurt Zouma pulled off a fine recovery to thwart Mane, who had appeared clear and away, but then Chelsea struck, pouncing on the Reds’ rare miscue playing out from the back.
Willian had hardly finished kicking himself for firing straight at Adrian when he found the ball back at his feet on the edge of the Liverpool area.
Willian latched onto the gift and stubbed another strike on goal, and another straight down Adrian’s throat. The 33-year-old Spanish keeper should have saved with ease, but could only fumble the ball into the net.
However strong the protest that he was unsighted, Adrian should still have mopped up the danger. Instead a howling error handed the hosts the advantage.
To add insult to injury, Chelsea’s under-fire keeper Kepa then jumped back to top form. The Spain star’s triple save to deny Mane, Origi and Curtis Jones proved just as pivotal in assuring Chelsea’s interval lead as Willian’s fortunate strike.
The luck that kept Lampard’s men ahead at the break did not extend to the injury front however, as Kovacic hobbled off in a worrying new fitness concern.
And no sooner had the second half begun than Willian left the field in some distress too.
Mason Mount quickly matched the pace and intensity of the contest in a boost to the Blues however, and the talented young midfielder rattled the bar with a high-quality whipped free-kick.
The Blues continued in the same vein and Barkley conjured a sumptuous break and finish to solidify the home side’s dominance.
Pedro should have added a third moments later after finding himself clean through on goal, but could blast at the diving Adrian’s legs.
Giroud should have killed the tie too, but Adrian palmed his close-range effort onto the bar when the France striker should really have hit the net.