Klopp warns Liverpool to beware 'super-disciplined' Atalanta
Atalanta knocked out Portuguese side Sporting Lisbon in the previous round but have won just two of their last nine matches in all competitions.
Nevertheless, Klopp expects Atalanta, managed by long-serving boss Gian Piero Gasperini, to pose Liverpool problems.
"There are now only great teams left in the competition," Klopp told a pre-match press conference on Wednesday.
"It's really outstanding and we know what Atalanta are all about. Gasperini is doing an incredible job there for years and years and it's difficult to play against Italian teams, always was.
"Tactically they're super disciplined and super dangerous in a lot of areas, so we have to be at our best to get into the next round over these two legs."
Klopp, in his last season at Anfield, said there was a chance Diogo Jota, Trent Alexander-Arnold and Alisson Becker, all injured since February, could feature against Atalanta.
"Obviously we didn't rush it with the boys," said Klopp. "That means they did a lot of training by themselves. Diogo and Trent worked as a group since two, three weeks and could do really proper training. It was very good yesterday (Tuesday).
The German added: "It's always a challenge to reintegrate the guys but, with the quality they have, obviously it should be a bit easier and we will use them in the next days and weeks. What it means for tomorrow, I didn't make a decision yet."
Meanwhile, Liverpool midfielder Harvey Elliott insisted he was ready to step up into a starting role rather than merely be regarded as a substitute.
"I want to be the player walking out, rather than coming on," said the 21-year-old Elliott.
"That doesn't mean I'm not grateful for coming on the pitch, I'm very grateful for every opportunity that I get in a Liverpool shirt, but for me it's about kicking on for myself and cementing my spot in the team.
"I'm not a kid anymore, I'm a man, I'm growing up quickly, I feel like I need to take responsibilities into my own hands. If that means knocking on the gaffer's door, it's going to have to happen. But, at the same time, I do need to wait for my opportunities, I do need to be patient."