Atalanta's Josip Ilicic and Robin Gosens scored quickfire second-half goals to give them a comfortable 2-0 win over a toothless Liverpool, who barely managed a shot on target, in their Champions League Group D clash at Anfield on Wednesday.
Having recently complained about fixture congestion and its effect on his injury-hit squad, Liverpool boss Juergen Klopp made a number of changes but the result was a flat performance as the home side struggled to get out of second gear.
Atalanta, who had been mauled 5-0 by Liverpool in Italy, took full advantage, punishing the hosts' sloppiness with two goals in four minutes after the break.
Though Liverpool still lead the group on nine points, both Atalanta and Ajax Amsterdam, who beat bottom side Midtjylland 3-1, are now two points behind with two games left to play.
"My only interest at the moment is that we got the thumbs-up, nobody injured, recover immediately ... the boys are completely disappointed, frustrated, but really, we don't have time for it, to be honest, just get fresh legs as quick as possible and go again," Klopp told BT Sport.
The German welcomed back Egyptian forward Mohamed Salah, who had missed their Premier League win over Leicester City after testing positive for COVID-19 while on international duty, but also fielded three teenagers in a much-changed side.
Rhys Williams and Neco Williams were deployed in defence with fellow 19-year-old Curtis Jones just in front of them, and Atalanta exploited their lack of experience early on to create several half-chances in the opening 45 minutes.
Atalanta were far better in defence than they had been when Liverpool took them apart in their previous Champions League outing.
The hosts, meanwhile, struggled to get the ball up to their attacking trio of Salah, Sadio Mane and Divock Origi, and it took until the 44th minute for Salah to threaten with a shot that flew just wide.
Klopp looked set to reshuffle his pack on the hour mark by bringing on Roberto Firmino, Fabinho, Diogo Jota and Andy Robertson, but his side went behind before he could make the switches as Ilicic scored with a deft volley from an inswinging cross from Alejandro Gomez.
Liverpool made their changes but they were soon two goals down as Gosens was left unmarked to volley home Hans Hateboer's knockdown from close range in the 63rd minute.
With their attack still misfiring, Liverpool could not rebound though as Atalanta became the first Italian side to win at Anfield since Udinese in the Europa League in October 2012.
"We had a great game tonight, we managed to play our football," Atalanta coach Gian Piero Gasperini told Italian TV. "We played better this time and we played quality football as well as being solid throughout."