Liverpool manager Brendan Rodgers challenged his players to improve their concentration after seeing Udinese come from behind to win 3-2 at Anfield.
The Italians scored three second-half goals to transform the Europa League tie after Liverpool dominated the opening 45 minutes to lead 1-0.
"We concede goals too easily," Rodgers said. "It's an area we have to work on.
"We were very good in the first half but we lost concentration and became lazy and found ourselves 3-1 down."
This was a third successive home defeat for Liverpool but Rodgers can see the areas his side must improve on ahead of the visit of Stoke in the Premier League on Sunday. "I thought the team worked very well but we can't have to score three, four or five goals to win games," Rodgers said.
Liverpool completed nearly four times as many passes at their Italian opponents at Anfield but having seen Antonio Di Natale equalise 32 seconds after the restart, they conceded two further goals in three second-half minutes as the match slipped away.
Rodgers introduced Luis Suarez, Steven Gerrard and Raheem Sterling as Liverpool attempted to rescue a point and although the Uruguayan striker pulled a goal back, it was too little too late.
"We injected some quality into the game in the last 15 minutes or so and got a goal back but we are just disappointed that after such a good first-half performance we have given away such poor goals," Rodgers added.
The result leaves the Premier League club third in Group A, a point behind Udinese and Russian side Anzhi Makhachkala after two games.
"It is still very tight and there are some excellent teams in our group," Rodgers said.
"For us it is important to qualify of course, but it is also an opportunity to give some of our younger players a chance."