The Socceroos fell to a 2-1 loss at the hands of France in their opening match, but Van Marwijk has decided against making any changes.
Arzani is the tournament's youngest player and looked sharp from the bench against France, but Van Marwijk has kept the 19-year-old in reserve today.
Nicolai Jorgensen will start up top for the Danes, with support being provided by Christian Eriksen, Pione Sisto and Yussuf Poulsen, who netted the winning goal against Peru to leave his side in a strong position.
A draw in Samara will keep Australia's hopes of progression alive, but defeat would end their World Cup campaign after just two matches.
Denmark: Schmeichel; Dalsgaard, Kjaer, Christensen, Larsen; Delaney, Schone; Poulsen, Eriksen, Sisto; Jorgensen
Subs: Braithwaite, Cornelius, Dolberg, Fischer, Jorgensen, Knudsen, Krohn-Dehli, Larager, Lossl, Ronnow, Vestergaard
Australia: Ryan; Risdon, Sainsbury, Milligan, Behich; Jedinak, Mooy; Leckie, Rogic, Kruse; Nabbout
Subs: Jones, Vukovic, Degenek, Meredith, Cahill, Jurman, Irvine, Nabbout, Luongo, Petratos, Arzani, Maclaren
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