The Reds won 3-2, though Karius' latest error will dominate the post-match reports.
On 71 minutes, Oliie Norburn drove a 25-yard free-kick which was firm, but straight at the goalkeeper's midriff.
Inexplicably he fumbled and spilled the ball and debutant Jonny Smith gratefully slid the rebound past him.
Afterwards, Reds boss Jurgen Klopp said: "Nobody likes that goal, but if we talk about the second goal – I think it was Millie's fault together with Chirivella. Two brilliant footballers make this mistake, which one was bigger? I would say the mistake of the two boys, but we don't talk about it.
"Loris concedes that goal, but we cannot start a story always after each mistake. Mistakes will happen; I don't like it, he doesn't like it, but it will happen, so let's carry on and make the best of all these situations by learning from them. That's how it is."