Coach Graham Arnold wants his Socceroos to get in the face of Lionel Messi, but not dwell on the Argentinian ace for too long.

The masterful Messi looms large for the unheralded Australians in their knockout battle with Argentina at the World Cup in Qatar on Saturday night (0600 AEDT Sunday).

“The thing is, if you focus too much on Messi, then you’re forgetting about the other players,” Arnold told reporters.

“And if you watched the game, I think Poland focused too much on Messi.

“Whoever is playing, pick him up. It can’t be just one, it can be five (players).

“But it’s not just about stopping him. They have got some very good players.”

The Socceroos enter the fixture at Doha’s Ahmad bin Ali Stadium as rank outsiders to halt Messi’s bid to capture an elusive World Cup.

The Australians are into the round of 16 for just the second time, following the 2006 Socceroos who fell to Italy 1-0 after a contentious stoppage time penalty.

Under Arnold, the Aussies have won two games at a World Cup finals for the first time; ditto for two consecutive clean sheets.

And Arnold said his advancing Australians were getting greedy.

“We want more,” he said.

“This is a dream come true, playing against Lionel Messi in a World Cup.

“I don’t think anyone expected us to even win a game. And then to win two in one World Cup, it’s amazing.

“But as I said to the boys, you don’t get these opportunities often in life.

“So what are you going to do about it? Are you just going to let it ride? Or are you going to do something more and special.

“It’s the Aussie DNA: keep going.”

Arnold was blunt when asked just how Australia, ranked 38th in the world, could upset the world No.3 Argentinians.

“Get in their faces. Don’t give them time,” he said.

“Stopping their main players from getting on the ball is going to be crucial.”

Which leads Arnold back to Messi, the 35-year-old who has won world football’s most prestigious individual award, the Ballon d’Or, a record seven times.

Arnold himself crossed paths on-field with another acclaimed Argentinian legend, Diego Maradona, during their playing days.

Who’s best, Messi or Maradona?

“Ahh, mate,” Arnold said.

“Let’s just say both.

“It’s just so crazy how similar they are, left footers and the same style of players, and they’re both incredible players.

“To compare different generations is all too hard … they go down as two of the greatest players ever in my lifetime.”