Chelsea 3 Derby County 2
Frank Lampard's Derby scored two own goals as Chelsea earned a hard-fought 3-2 Carabao Cup win at Stamford Bridge.
Chelsea's record goalscorer was serenaded throughout a night which must have felt all the more surreal because of the way the fourth-round match unfolded.
Lampard must have sensed an opportunity missed as Derby conceded three times in the first half and could only reply twice, exiting as Chelsea advanced to the quarter-finals.
A penalty shootout win over Manchester United - managed by Lampard's former mentor at Chelsea, Jose Mourinho - set up the tie at the Rams boss' former stomping ground.
Fikayo Tomori, on loan from the Blues, scored an own goal after five minutes, but lifelong Chelsea fan Jack Marriott equalised within four minutes.
A near identical own goal - another Davide Zappacosta cross, this time sliced into his own net by Richard Keogh - restored Chelsea's advantage after 21 minutes.
The lead was short lived as Mason Mount, another Blues loanee, laid on Martyn Waghorn's leveller after 27 minutes.
Derby found themselves behind again before half-time, as Cesc Fabregas netted much to the annoyance of the visitors who felt there was a foul in the build-up.
Substitute David Nugent struck a post in the 89th minute as Derby came close to a third equaliser, but Chelsea survived and progressed.
England boss Gareth Southgate called Mount into his squad during the recent international break and would have been pleased to witness the 19-year-old feature - and impress.
Chelsea denied granting Derby permission to field Mount and Tomori was a favour to Lampard, who scored 211 goals in 648 appearances over 13 years, saying it was more a test of character for the players.
Tomori's test was enhanced when he diverted an innocuous Zappacosta cross into his own net after mis-kicking an attempted clearance. Thereafter he performed well.
Derby levelled swiftly as Tom Huddlestone pounced on Gary Cahill's pass to win the ball off Fabregas and fed Marriott to his left. The forward finished brilliantly.
The Rams might have led had Waghorn shown the same composure. Instead he tripped over his own feet and shot straight at Willy Caballero.
Chelsea's second was a near replica of their first, this time Keogh the unwitting defender.
Derby responded once more. This time Mount found himself in space in the left of Chelsea's area, crossing for Waghorn to simply tap in at the back post.
Lampard shook his head in apparent disbelief at the cup tie unfolding before him.
Ruben Loftus-Cheek, another player Southgate was watching, tumbled over the advertising hoardings after a shoulder-to-shoulder with Scott Malone and that might have subconsciously influenced referee Jon Moss in not awarding Derby a free-kick when Zappacosta and Tom Lawrence had a similar physical challenge on the touchline.
Instead of a foul Zappacosta took a quick throw-in and the late arriving Fabregas tucked in a few moments later. It was a Lampard-esque goal and Derby's protests were dismissed by Moss.
Scott Carson saved a half-chance from Alvaro Morata and then palmed away a header from Cahill.
Maurizio Sarri sent on David Luiz, who was caught out by the speeding Marriott. His shot was palmed on to the roof of the net by Caballero.
A Mount shot went narrowly wide off Cahill as Derby went close again.
Carson saved Morata's header from Willian's corner and Derby had two chances to level in quick succession.
Keogh showed a striker's instinct to bring down Jayden Bogle's long pass, only for Caballero to stick out a hand.
The Blues goalkeeper saved Mount's snap shot soon afterwards and then from Marriott.
Nugent beat Caballero, but the ball rebounded off the post as Derby were beaten.