Defeat at Chelsea was a third on the bounce for the Reds, with Aldridge admitting he's concerned.
He wrote for the Liverpool Echo: "Please excuse me if I keep banging on about the same thing. But Liverpool really do need to remember how to keep a clean sheet.
"That’s the main difference between ourselves and Arsenal now. The Gunners aren’t really pulling up any trees, but their ability to keep things tight at the back means they always have a chance of winning games, which they are now starting to do.
"They are the real worry for Liverpool in terms of the title race. Manchester City are dangerous and will always be a threat, but Arsenal are far more settled regards line-up and what they are trying to do.
"I saw what people did after beating Liverpool and new signings cannot ignore it
"That’s the complete opposite to us at present. We don’t look like we’re ever going to keep a clean sheet at the moment.
"We look so vulnerable whenever the opposition gets beyond the halfway line and we keep coughing up simple chances – and big chances at that.
"The first line of the defence is always the forwards, but they don’t seem capable of doing much pressing at the moment."