David Edgar got the lone consolation goal for Newcastle.
Toon boss Joe Kinnear admitted their lack of strength in depth was reflected in the scoreline.
"We were short of about six or seven players," Kinnear told Sky Sports.
"Everything else that could have gone against us went against us today, even from when we had just got a settled back four, we lost two at Wigan, so we had to change things round a little bit.
"Of course, we had to play one of the best teams I've seen in a long while and you've got to take your hat off to Liverpool.
"They were always in command, but I thought we had a lifeline when we got back to 2-1, but to be fair to them they could have put the game to bed in the first half.
"We looked a little bit tired at times as well with the second game coming so quickly. It shows we are struggling as far as strength in depth is concerned with players.
"When you've got seven key players missing it's never going to be easy, irrespective of who you play against.
"Unfortunately, we had to play an in-form side today. Steven Gerrard was magnificent and fair credit to them, but I would have liked to have gone in with the best 11 we had."