"When we talk about this Liverpool team, we talk about the front three," said Carragher on Monday Night Football. "It's almost like they come as a package.
"The reason I say that Liverpool's front three is unique is not that they are better than other front threes, it's how long they've stayed together.
"They are all getting to their late 20s and sooner or later that front three will have to be broken up.
"You can't, in two years' time, say 'we're going to buy a new front three' and replace them all. It will change over time.
"I am still confident Mane and Salah will start scoring goals again. I must say I am worried for Firmino.
"He has never been seen as 'the' goalscorer. That is the responsibility of the other two, but he is there to chip in.
"When they are not scoring, he has to be a bigger goal threat.
"Yesterday (during the 0-0 draw with Manchester United) he had a couple of chances but did not quite strike the ball right."