Former Denmark goalkeeper Thomas Sorensen feels the side need to "muscle up" as they steel themselves for the physical threat posed by Australia.
Age Hareide's men were perhaps fortunate to defeat Peru in their World Cup Group C opener, Yussuf Poulsen netting the only goal after Christian Cueva had missed a penalty for their opponents.
A win over the Socceroos in Samara on Thursday, combined with Peru failing to beat France, would see Denmark into the last 16 - a feat they have not managed since 2002, when Sorensen was in goal for a 3-0 defeat to England in Japan.
And the former Sunderland, Aston Villa and Stoke City keeper, who won 101 caps for his country, has warned Hareide's side to be ready for a combative contest.
"Today will be a good indication [of how far Denmark can go], if they can play more free," he told Omnisport.
"Like how they showed in qualifying and against Ireland in the play-offs and against Poland when they beat them 4-0 in Copenhagen.
"If they do that I can see them being a test for any team, but they need to play better and play faster and muscle up a bit.
"They talked before the Peru game about their physical strength compared to them but I thought Peru came out looking strongest, so that needs to change because Australia are not going to be easy, that's one of their strong sides is being physical and the fight they always come up with."
Sorensen believes Denmark need to get star man Christian Eriksen more heavily involved, while hoping that the opening win will have eased the burden on the players' shoulders.
"I'm hoping we can get him more into the game because it will be difficult the way Australia set up, they're very well drilled by Bert van Marwijk and they've been working on limiting that space from the defence," he added.
"They work across the pitch and stay in the same shape, so it'll be hard for Eriksen to find that space but it'll be vital for Denmark to get him involved and get him on the ball as much as they can, that'll be key.
"Hopefully they go into today with a lot more confidence and feel like the pressure is off.
"They're probably aware Australia are not as much of a threat on the counter as Peru were, not as quick and sharp, and hopefully they can get their game going a little bit better.
"Everyone was happy we won the first game but we have to also be realistic that, if we want to go far in this tournament, that wasn't good enough and the players have come out and said that we discussed it after the game and that needs to change."
|Guardiola happy with Mahrez and Man City despite loss|
|Dodgers top Brewers in Machado´s debut|
|Raptors GM apologises to DeRozan after Spurs trade|
|Manchester City 0 Borussia Dortmund 1: Gotze spoils Mahrez´s debut in ICC opener|
|United fans keeping De Gea at Old Trafford – Herrera|
|Keita: I turned down Barca and Bayern for Liverpool|
|Merritt stays ahead as rain halts Barbasol Championship|
|Roma had to sell Alisson to Liverpool, says Totti|
|Donald Trump: Kneeling players should be suspended without pay|
|Cardinals´ Carpenter makes history|
|Nationals pair Strasburg, Zimmerman activated from DL|
|Premier League-linked Plattenhardt feels at home at Hertha|
|Johnson expecting tough Granollers challenge|
|Good Luck at last! Colts quarterback fit for training camp|
|Haase humbles Rublev as Cecchinato charges on|
|Benzema hits back at ´crazy´ De Laurentiis over age jibe|
|Leeds Rhinos finally end winless streak in Super League|
|No freaky Friday for Spieth as he bounces back in round two|
|Double boost for Bouchard in Gstaad|
|Iconic Ronaldo to raise Serie A level - Roma´s Hamm|
|Brighton birthday boy March renews contract|
|Lamela hoping injuries are behind him after signing Tottenham extension|
|Where will I get my massage? - Roma´s Pallotta mocks UEFA ban|
|Rashid struck by Lightning amid speculation over Test recall|
|Major misses a mixed blessing for Fowler and Kuchar|
|Fleetwood, McIlroy and Spieth bare teeth as Kisner and Johnson lead|
|The Open 2018 diary: Fleetwood´s swinging in the rain, but it´s a slog for McIlroy|
|Fees agreed as Fabri closes in on Fulham move|
|Neymar and Mbappe have a very good relationship, claims PSG president|
|Boufal joins Celta Vigo on loan from Southampton|
|Leicester sign Ward from Liverpool amid Schmeichel speculation|
|Kisner philosophical after run-in with the Barry Burn|
|Gattuso unsure of Bonucci future|
|Verdasco, Gasquet advance but Ruud´s run is over in Bastad|
|James to remain at Bayern Munich, says Rummenigge|
|Texans QB Watson expects to be fit for training camp|
|Torpedo Moscow deny cancelling player´s contract over racist abuse|
|Napoli decry Cavani, Di Maria rumours as fake news|
|Kisner feels the Burn, Spieth on the surge|
|Woods: I could have cleaned up my round|
|Lille swoop for free agent Fonte|
|Sagan completes hat-trick after bunch sprint|
|´Amateur´ DFB needs Lahm´s help - Rummenigge|
|Horner expects Ricciardo new deal ´pretty quickly´|
|Diakhaby swaps Monaco for Huddersfield|
|Tottenham´s Lamela signs to 2022|
|Atletico´s Rodrigo excited to wear Simeone´s 14|
|F1 Raceweek: Red Bulls steal show from Mercedes but Ricciardo to start from back|
|Fakhar hits historic double hundred as Pakistan thrash Zimbabwe|
|Roma president Pallotta hit with three-month UEFA suspension|
|Hamburg extend contract of coveted youngster Jann-Fiete Arp|
|Steady start for Kisner as Woods endures mixed day at Carnoustie|
|Zach Johnson: Dustin comparisons are unfair|
|Neymar backs Tite for Brazil despite World Cup failure|
|Vinicius wants to play with ´idol´ Neymar but Perez calms transfer talk|
|One hundred not out for Els at The Open|
|Magnificent Maharaj takes eight wickets to stymie Sri Lanka|
|If I lose I´ll go down swinging - McIlroy ready for Carnoustie battle|
|UEFA confirms AC Milan reinstated to 2018-19 Europa League|
|Fleetwood: Open Championship is the one for me|
|Canberra coach Stuart brands bunker ´waste of time´ after controversial Cronulla loss|
|Son signs five-year Tottenham extension|
|Fleetwood cards fine 65 to share Open lead|
|WATCH: Evra belts out Bocelli in Ronaldo welcome video|
|I´ll always carry Roma in my heart, says Liverpool signing Alisson|
|CAS overturns AC Milan´s Europa League ban|
|McIlroy and Johnson on the move as Woods troubles Carnoustie spectators|
|Caleta-Car race won by Marseille|
|Hurricanes hold off Chiefs to reach final four|
|Bairstow: Unfair to compare England Test and ODI teams|