Ahead of kickoff, banners with the words "GOAL AFTER GOAL, GAME AFTER GAME" and "FOREVER A BLUE, ALWAYS A LEGEND" flanked a giant image of Lampard in the Matthew Harding Stand, emblazoned with the number 211 - his peerless goal tally for Chelsea.
England midfielder Alli provided the assist for the second goal but West Ham's Arthur Masuaku was at fault as he fluffed an attempt to block the pass, leaving Son to slot home in the 54th.
When, after all, have Chelsea kicked off a tie with 13 of their own players on the pitch from the start, as well as their most prolific scorer overseeing the opposition from the dugout? With barely five minutes on the clock, as if spooked by a scary outfit in the crowd, he took his eye off a cross, scooping the ball from his left toe onto his right shin and back into his own net.
Key Stat: Ruben Loftus-Cheek has scored twice as many goals in his past two games than he did in his first 35 for Chelsea.
"And then when I first came here, with Jose, the first target was to win the League Cup".
This fourth-round clash provided an opportunity to do so and Lampard was serenaded throughout by Chelsea supporters, and he responded by acknowledging them and the Derby fans at the end.
You can see how much the Chelsea fans love him, the Derby fans love him.
The first was from the Rams' on-loan Chelsea defender Fikayo Tomori, who played against his parent club along with Mason Mount, and the second by Richard Keogh.
Both Chelsea and Derby have enjoyed good starts under their new managers with the Blues now unbeaten in the Premier League and Derby sixth in the Championship. Chelsea won 6-1 on that occasion as the Rams were on they way back down to the Championship. Unlucky Tomori. If you've watched him play a few times, you'd know he is better than Christensen.
Chelsea are still unbeaten in domestic competition this season, and despite their potential absentees they will be looking to come through against Derby and move into the quarter final of the competition.
Lampard's Derby beat Manchester United and with luck, could have come out on top against another top-six Premier League team.
Maurizio Sarri would still have been unimpressed at the lack of control his team had exerted in that frenetic period, though they had more authority thereafter and, certainly, more control of possession.
It will be the Blues' third match in the space of six days, having beaten BATE Borisov and Burnley in the Europa League and Premier League respectively.