Ferdinand told BT Sport: "I don't think they've had a clean sheet in the Premier League this season. That would be a concern for me, especially against the top teams.
"What I would say is attacking football and for a fan to go and watch a team at the moment Liverpool are the team to go and watch.
"Klopp's got them playing with a great intensity going forward, some beautiful football.
"Lallana has got four in four now, Mane's involved in all the good play, Coutinho behind that.
"They've got great attacking prowess, it's just defensively as a unit I think they've got to transfer that balance, they've got to have that fine balance between defence and attack."