The Reds confirmed last week that the Dutchman had sustained ACL ligament damage against Everton.
"He's a massive presence on and off the pitch, in the changing room, everything," Alexander-Arnold told Liverpoolfc.com when asked about Van Dijk's absence.
“His communication and leadership is massive for us back there, he's probably the leader of the back four and obviously without him it's a bit strange because this is probably the first time and the first spell where we haven't had him since he's came in.
“So it's a bit weird for us but we want to adapt and adjust and I think in the two games we've been without him - well, three if you include Everton - we've shown how good we are defensively.
“Fab's stepped up and done an amazing job in there [and] Joey G [omez] is stepping up and leading as well.
"So even though it's disappointing not to have Virg, it's also an opportunity for us to come together as a back four and show our leadership and show that even though Virg is a big miss, hopefully we won't miss him as much as everyone potentially thinks."