Rio Ferdinand says Liverpool cannot be compared with Manchester United's great side of 2008 unless they win back to back Premier League titles.
Jurgen Klopp's side lifted the Champions League last season, a feat Ferdinand achieved with United in 2008.
But in the same period, the Red Devils reeled off a host of title triumphs - three in a row between 2006 and 2009.
Liverpool look set to lift the Premier League trophy for the first time in their history after pulling 13 points clear of the chasing pack.
Yet despite going a year unbeaten, Ferdinand says they must win then defend the Premier League before they can be compared to his crop of United greats.
During a Q&A on his Twitter account, Ferdinand was asked: "How would you compare this Liverpool team with the United Champions League winning team in 2008?
He replied: "Need to win back to back league titles before being compared but there’s no denying they’re on route to being great team!"
Liverpool have been tipped to match Arsenal's historic Invincibles season by going the entire season unbeaten.
But skipper Jordan Henderson insisted after beating Sheffield United that they are only focused on securing the title.
Asked if he was motivated by beating Arsenal's record, Henderson said: "Not really. I am not really bothered about that.
"I am bothered about next game and next challenge and see where that takes us come May."
Liverpool having won all their games in the Premier League apart from a 1-1 draw away to Manchester United - but Henderson insists they can get even better.
"The performance level has been really high for a long period of time," he said. "We want to continue that, keep doing the things we are doing, keep improving and keep concentrating on the next challenge.
"I still think we can improve. The last 10 or 15 minutes they had a good chance. We can't afford to give teams those chances. Overall the intensity was really good. We have coped well and need to improve for the derby on Sunday."
