The Liverpool manager was not too happy with his left-back's positioning in stoppage time.
Liverpool manager Jurgen Klopp has suggested to BT Sport, as quoted by BBC Sport, that he felt left-back Alberto Moreno was to blame for his side conceding a 92nd-minute winner against Villarreal on Thursday night.
The Europa League semi-final first leg at El Madrigal appeared to be petering out into a goalless draw until an attack from the home side on the counter opened up the visitors' defence for the only goal of the game.
There were appeals for offside from goalkeeper Simon Mignolet and his defence, but replays showed that goalscorer Adrian Lopez was clearly onside when he tapped home from Denis Suarez's ball across goal.
Moreno had only minutes earlier missed a good late chance when he made a lung-bursting run through the Villarreal half before firing high and wide when off-balance.
Speaking to BT Sport after the game, Klopp said he was pleased with the general level of performance from his side but questioned the defending of Moreno for the match's pivotal moment.
The German boss said, as quoted by BBC Sport: "Of course I'm not too happy with the goal we conceded in the last second. Counter attacking in the 92nd minute makes not much sense but it is only the first leg. It is 1-0 and they have to come to Anfield where we know how strong we are.
"We had our moments, we defended really good. This race is not over. If we had enough players in around the box it was no problem but they played this one chip ball over Kolo, I don't know where Alberto was in this moment but that was the only big mistake we made in this game and they scored with it.
"90 minutes played, 95, we will play at Anfield and that is a different game then."
Liverpool are looking to reach their first European final since the famous night in Istanbul in the 2005 Champions League final, but will have to do things the difficult way after the late setback.
However, the tie is still in the balance, and their remarkable comeback against Borussia Dortmund in the last round will surely have given them the confidence to overcome any deficit.