Sky Bet League Two Plymouth ground out a goalless draw at Anfield as the youngest team in Liverpool's history discovered they still have plenty to learn.
A Reds team containing five academy graduates came up against a green wall as Argyle manager Derek Adams succeeded in making life as difficult as possible for the hosts in their FA Cup third-round encounter.
The tactics were understandable for a side second in League Two coming to a club second in the Premier League who score for fun at home, and Plymouth now have a chance of causing an upset at Home Park.
A replay is something Jurgen Klopp could have done without in a month which contains a two-legged EFL Cup semi-final against Southampton as well as a trip to Manchester United and the visit of league leaders Chelsea, but it was not entirely surprising considering the team he put out.
Liverpool's side had an average age of 21 years and 296 days - even taking into account the presence of captain Lucas Leiva, 30 on Monday - with almost half the team coming through the club's academy.
Lucas was making his 329th appearance for the Reds - the same number as all his other 10 team-mates combined - but Liverpool really needed the know-how in a more advanced position than central defence.
Alongside him was Joe Gomez, playing his first match for 465 days and his first appearance under Klopp after a serious knee injury, and it proved a more than comfortable return for the 19-year-old.
Eighty per cent possession for Liverpool in the first half told its own story as Plymouth, after having an initial go, retreated into damage-limitation mode putting at least nine outfield players behind the ball.
Sheyi Ojo, one of five teenagers in the home side, fluffed a close-range header from Emre Can's deflected free-kick while the quick feet of Ben Woodburn, the club's youngest ever goalscorer after his strike against Leeds in November's EFL Cup tie, created a couple of chances with goalkeeper Luke McCormick saving one.
Divock Origi's attempts to out-muscle Gary Millar were judged unfair as the Belgium striker put the ball in the net and that was the closest Liverpool came in the first half.
A similar pattern continued in the second half - although Plymouth did manage a shot on target with Graham Carey's free-kick comfortably held by the otherwise unemployed Loris Karius - with Ojo heading wide.
Within a minute of coming on just past the hour Daniel Sturridge rolled a shot narrowly wide and then proceeded to try to win the game single-handedly as, after almost picking out Ojo with a delicate chip, he headed over and fired into the side-netting.
Klopp sent on Roberto Firmino and Adam Lallana in an attempt to break the deadlock and Origi headed wide, but the visitors held firm to earn their reward.