"Disappointed that we did not go through but not frustrated or angry. Now we can focus on the league and that's what we will do," Klopp told reporters.
Last season's runners-up Roma advanced to their fourth European semi-final in a row.
Atalanta have a chance to make history on Thursday as they welcome Liverpool to Bergamo with one foot in the Europa League semi-finals thanks to a stunning first-leg win at Anfield.
Jurgen Klopp was headed for a glorious send-off in his final season at Liverpool just a few weeks ago, but talk of a potential quadruple is now long forgotten as the Reds have come off the rails.
"It just was a really bad game, oh my god. We started well, really well, and then didn't continue. I think even before they scored, we just lost the plot a little bit, we were everywhere and nowhere," Klopp told reporters.
Atalanta knocked out Portuguese side Sporting Lisbon in the previous round but have won just two of their last nine matches in all competitions.
Leverkusen head into Thursday's home first leg against West Ham in the Europa League quarter-finals unbeaten in 41 matches this season, with 36 wins and five draws.
Jurgen Klopp's Liverpool, who are still in contention to win a quadruple this season, will entertain Atalanta at Anfield on April 11 and go to Italy a week later for the return.
AC Milan, Marseille, Roma and West Ham were among the other sides to also book their place in Friday's quarter-final draw.
"Disappointed that we did not go through but not frustrated or angry. Now we can focus on the league and that's what we will do," Klopp told reporters.
Last season's runners-up Roma advanced to their fourth European semi-final in a row.
Atalanta have a chance to make history on Thursday as they welcome Liverpool to Bergamo with one foot in the Europa League semi-finals thanks to a stunning first-leg win at Anfield.
Jurgen Klopp was headed for a glorious send-off in his final season at Liverpool just a few weeks ago, but talk of a potential quadruple is now long forgotten as the Reds have come off the rails.
"It just was a really bad game, oh my god. We started well, really well, and then didn't continue. I think even before they scored, we just lost the plot a little bit, we were everywhere and nowhere," Klopp told reporters.
Atalanta knocked out Portuguese side Sporting Lisbon in the previous round but have won just two of their last nine matches in all competitions.
Leverkusen head into Thursday's home first leg against West Ham in the Europa League quarter-finals unbeaten in 41 matches this season, with 36 wins and five draws.
Jurgen Klopp's Liverpool, who are still in contention to win a quadruple this season, will entertain Atalanta at Anfield on April 11 and go to Italy a week later for the return.
AC Milan, Marseille, Roma and West Ham were among the other sides to also book their place in Friday's quarter-final draw.
Liverpool remain on course to send Jurgen Klopp off with a quadruple.