LIVERPOOL, England -- Jurgen Klopp described Alisson's stoppage-time intervention against Napoli on Tuesday as a "lifesaver" as Liverpool reached the knockout rounds of the Champions League.

Liverpool will be in a draw for the round of 16 on Dec. 17 after Mohamed Salah's 34th-minute goal proved to be the difference at Anfield in the must-win tie.

But, with a Napoli goal sending Liverpool into the Europa League, Alisson, the £65 million summer signing, made a crucial save to deny Arkadiusz Milik from close range.

"The goal Mo scored -- what a goal, unbelievable. And the save Ali made -- I have no words for that," Klopp said at his post-match news conference.

"That was, of course, a lifesaver tonight. I'm really proud what the boys did tonight."

Klopp added: "It was not only one save. He had a lot of things to do tonight.

"How cool and calm he was with the ball helps us a lot in our build-up situations. When he comes out for crosses he is outstanding. And, yes, that save was just incredible.

"But if we don't defend the whole pitch like we defended, Ali cannot make 20 saves like the last one.

"He did it. ... Incredible, unbelievable. I never saw something similar. But still he needs the other boys around."

The win means Liverpool, last season's finalists, have now progressed to the knockout stages in back-to-back Champions League campaigns for the first time since 2008-09.

Klopp was left delighted with the performance from his side, who are now unbeaten in their last 19 European matches at Anfield.

"I'm still full of adrenaline," the Liverpool manager said. "This game was just amazing. It was outstanding, unbelievable.

"The boys played their whole hearts on the pitch -- I'm not sure it's right saying. With each part of their body, they were in that game. Our offensive defending, our offensive pressing was some of the best I've ever saw.

"The intensity we played with was just difficult to deal with. Yes, we could have scored more often but the 2-0 doesn't help a lot.

"The most difficult period was after the 1-0. You could see this little bit of relief and then Napoli was there. That made the game so intense. We knew at half-time that you cannot change the tactics and say: 'Let's sit a bit deeper.' In that moment, they are not to defend anymore because they do it really so well.

"We had to do it like how we did it in the first half."

Liverpool finish second in the Group C behind Paris Saint-Germain, meaning they can be paired with holders Real Madrid in the last 16.

"We have no say in that," Klopp said. "We wait for the draw -- no problem with that.

"Until 7:55 tonight, I was really not sure that we will be in the draw still and now we are in it. How could I sit here and ask for any team? I don't care.

"We are second in the group, so we will have an outstandingly strong opponent. That's it."

Meanwhile, Liverpool have a number of injury concerns to their defence after the Napoli victory, and sources have confirmed to ESPN FC that Joel Matip went to hospital following the match for tests on his shoulder injury sustained in the final seconds.

Trent Alexander-Arnold hobbled off in the 90th minute with an apparent foot issue, while James Milner was suffering from cramps.

"Trent got a knock on his foot, we are not sure about what exactly it is," Klopp said. "It is painful.

"Millie had cramps -- I hope it was only cramp. That was it, I don't know anything else."