Liverpool was undermined by more defensive sloppiness and a missed penalty in a 2-2 draw with Sevilla in a Champions League match that featured two sendings-off and a spat between coaching staff at Anfield on Wednesday.
Joaquin Correa earned a point for Sevilla by curling home from just inside the area in the 72nd minute after Liverpool switched off at a throw-in, allowing Luis Muriel to receive the ball and run through unchecked.
Sevilla's opening goal in the fifth minute also arose from a defensive error, with Liverpool center back Dejan Lovren letting a low cross go under his boot and Wissam Ben Yedder was on hand to poke in at the far post.
Liverpool fought back to dominate the game and take the lead by halftime thanks to Roberto Firmino's tap-in in the 21st and Mohamed Salah's deflected shot in the 36th. Firmino missed a chance to make it 3-1 when he struck a penalty against the outside of the post in the 42nd after Sadio Mane was pulled back.
The Reds' attacking play was thrilling once again, but defensive uncertainty continues to plague the team. Only last weekend, Liverpool was thrashed 5-0 by Manchester City in the Premier League and the failure to sign a high-quality center back, such as Southampton's Virgil van Dijk, in the summer transfer window may turn out to be costly.
"We need to learn how to be dominant and not to give easy goals away," Liverpool manager Juergen Klopp said.
"A few players could not keep the level of the first half ... It wasn't about tiredness, it was about concentration."
Philippe Coutinho came on as a 76th-minute substitute for his first appearance of the season for Liverpool, following a summer that saw him put in a transfer request after his club rejected three huge offers from Barcelona.
The Brazil playmaker was given a warm reception from Liverpool's fans - before and during the game - but he didn't make a significant impact on the field and gave the ball away on a number of occasions.
Sevilla ended the Group E match with its coach, Eduardo Berizzo, in the stands after he was sent from the touchline by Dutch referee Danny Makkelie in the 60th minute for preventing Liverpool right back Joe Gomez from taking a quick throw. Berizzo angrily gestured to Klopp while being led away.
Gomez was sent off in stoppage time for collecting a second yellow card for a late tackle. And there was an altercation after the final whistle when Sevilla's physiotherapist, Pablo Fernandez, approached Klopp and shouted abuse at him, seemingly blaming the Liverpool manager for helping to get Berizzo sent off.
Klopp and Berizzo said they settled their differences in the dressing room after the match.
Both teams made it through to the group stage via the playoffs, with Liverpool - a five-time European champion - returning to the Champions League after a two-season absence. They are the favorites to advance to the knockout stage ahead of Maribor and Spartak Moscow, who drew 1-1 on Wednesday.