Exeter City 2-2 Liverpool
In what was an enthralling FA Cup tie at St James' Park, Liverpool's youngsters twice had to come from behind to earn parity against League Two outfit Exeter City.
The Anfield club had never previously lost to fourth-tier opposition in their history, but a side showing 11 changes from the Capital One Cup semi-final on Tuesday were within 18 minutes of exiting in the third round.
Tom Nichols and Lee Holmes had twice given Sky Bet League Two Exeter the lead, the second goal scored direct from a corner which goalkeeper Adam Bogdan somehow allowed to sail over his head and into the far corner of his net.
Jerome Sinclair had cancelled out Nichols' opener and then Brad Smith fired home to deny Exeter - 76 league places below Liverpool - a famous victory.
Liverpool's injury list meant changes were inevitable after their victory at Stoke three days earlier, especially with Premier League leaders Arsenal due at Anfield next Wednesday.
Klopp was without 13 players - seven of them with hamstring problems - and in the event he changed the entire team with Tiago Ilori, Kevin Stewart and Ryan Kent making senior debuts for a side which only had 34 Liverpool appearances between them in total this season.
Christian Benteke provided some seniority up front and the experienced Jose Enrique featured for the first time since an FA Cup tie against Bolton last January.
But Exeter must have been lifted by the sight of the Liverpool team sheet and Nichols was immediately keen to test Enrique's pace on a St James Park pitch which was bare in patches.
Nichols' early energy paid off when Alex Nicholls fed Jamie Reid down the right channel and the striker slid home his cross past a helpless Bogdan.
Klopp might have feared the worst for his youthful side but Liverpool were level within three minutes after Smith had made good ground down the left.
Liverpool were patient around the edge of the Exeter box and a mix-up between Troy Brown and Jordan Tillson allowed the highly-rated Sinclair to pounce for his first senior goal.
Joao Teixeira's shot was soon deflected wide but Liverpool escaped when Christian Ribeiro's cross evaded defenders at the near post for David Noble to fire over under pressure.
Liverpool had been neat and tidy for most of the first period and Stewart forced a save from Bobby Olejnik in the closing stages.
But it was Exeter who finished the half on top as Ribeiro headed wide from a Holmes cross with Bodan beaten.
Then, on the stroke of half-time, Exeter won a corner and Holmes' kick left Bogdan bemused as the ball beat him to restore the Grecians' lead.
Exeter had appeals for a penalty waved away when Ribeiro tumbled at the start of the second half but Olejnik preserved their lead with a stunning save from Benteke's point-blank header.
Nichols and Arron Davies went close to putting the tie beyond Liverpool but Exeter were beginning to show signs of fatigue and Smith levelled after 72 minutes.
Olejnik pushed out substitute Sheyi Ojo's cross straight to Smith and the Australian left-back finished firmly.
Liverpool now sensed a winner and Olejnik denied Teixeira, but Klopp had to settle for an Anfield replay in what is an already crowded January schedule for his team.