Jurgen Klopp says Liverpool let a three-goal lead slip to draw 3-3 with Sevilla on Tuesday night because they "stopped playing football" in the second half.
Liverpool missed out on the chance to secure their place in the knockout stages of the Champions League after a second-half capitulation at the Ramon Sanchez Pizjuan Stadium.
Klopp's side went into half-time 3-0 up courtesy of two goals from Roberto Firmino and one from Sadio Mane before Sevilla fought back after the restart.
Wassam Ben Yedder netted twice -- the second goal from the penalty spot after an Alberto Moreno foul -- before Guido Pizarro scored deep into injury time as Liverpool failed to clear a corner kick.
"It's a very good first half and not that good second half," Klopp told BT Sport. "We stopped playing football in the second half. We let them come back in the game. With this crowd behind their back, things like this can happen.
"We did it already the other way around. You like this when you can change the game and come back in the game. When you are the winning team then you should avoid it, and we didn't.
"We have a real weapon and that's playing football. We didn't do it in the second half until we conceded the second goal. After that, we came back and had our chances a little bit. We didn't use them, so they could do what they did in the last minute."
Despite holding a big lead, Klopp does not believe complacency crept into his players when they re-emerged for the second period.
"It was absolutely OK that we are confident after that first half," he added. "We were in two situations obviously too late in the second half -- not only Alberto, the whole formation was too late in this situation.
"That's obvious what we did. The real problem is that we stopped playing football. We had to close the game.
"3-0 is a wonderful result. There's nothing bad to say at half-time. But you have to stay in the game because 50 minutes is a long time -- you can score 10 times if you want.
"Our main mistake was that we didn't play football anymore. We wanted to control it, but we got too passive and a little bit too deep, so they had their situations. They fought back and that's a big credit to them. We had to do it different."
There was an element of history repeating itself as Liverpool led the 2016 Europa League final 1-0 at half-time only to lose 3-1 and six of the players who featured in Basel on that night played some part in Seville.
The character of Klopp's players has been called into question since then but the Reds boss does not believe it is an issue.
"We showed already fantastic mentality against Dortmund [staging a late comeback to win the Europa League quarter-final 4-3], we showed it in a lot of other games.
"Yes it was not perfect tonight but it's not a general problem. It just happened.
"Could we have done better? 100 percent. Do I think it's a mentality problem? 100 percent not.
"We opened the door for them, didn't close it, so they could score in the last minute. That's the story of the game.''
Liverpool need a point at home to Spartak Moscow in the final matchday of Group E to reach the last 16 of Europe's premier club competition, or for Sevilla to earn at least a point at Maribor in their final fixture.
"It feels like we lost, but we didn't lose," Klopp concluded. "It's a point and, obviously, Sevilla booked the points at Maribor already [with] how they celebrated in the moment.
"There are two games to go and it's still in our own hands. That's what we will know from tomorrow on, but in the moment it feels really bad."
Sevilla's comeback preserved their year-long unbeaten home record which had looked like crumbling in spectacular circumstances.
Coach Eduardo Berizzo delivered a rousing team-talk at half-time and it had the desired response.
"I told them that you had to play with your soul, that there is no mistake that could not be solved,'' he said.
"We talked about rectifying, showing the pride we have, and that if we got the goal soon it was possible.
"They had to go out generating a different energy and people would believe. The team came out and infected 50,000 people.
"We took the risk of going for the game, and that speaks of the football bravery of the players.''
Press Association was used in this report.