Absent Liverpool manager Jurgen Klopp was "delighted" as the youngest team in the club's history beat Shrewsbury to reach the FA Cup fifth round.
Klopp decided to miss the fourth-round replay because it fell during the Premier League's winter break.
A Reds side with an average age of 19 years and 102 days set up a tie at Chelsea with a 1-0 win.
"There was a message at half-time and at full-time [from Klopp]," said under-23s boss Neil Critchley.
"There was a message before the game that Chelsea away could be an opportunity for one or two of them and they put in a performance tonight."
There was at least one of Klopp's senior players in the sell-out 52,399 crowd, with James Milner offering his support sat behind the home dugout.
"He trained with us yesterday and he asked whether he could come along," added Critchley, who oversaw the game for Liverpool.
"He was giving words of advice, he was getting right behind the players. He was vocal in the dressing room. He was animated. He was vocal behind me, I could hear him."