Emerging Socceroo Keanu Baccus says it was surreal to not only rub shoulders with Lionel Messi, but bash them.

Baccus, a 24-year-old who arrived in Qatar with just one Socceroos cap to his name, spent much of the opening half of the World Cup knockout game locking horns with Argentina's captain.

And just seven minutes in, he laid a shoulder-to-shoulder bump on Messi which floored the global megastar.

Baccus also did what few players have managed during Messi's 1000 professional games: steal possession from a man renowned as an all-time great.

"Definitely surreal how things work out," Baccus told reporters.

"It was a great experience for me, I definitely know we can go toe-to-toe with these guys."

Baccus, who moved from A-Leaguers Western Sydney to Scotland's St Mirren this year, said he was not assigned a marking role on Messi.

"It was just how the game went," he said.

"He was always in that pocket where I was, and being close I pinched it a few times which was good.

"But he's a great player and got one in the end and that is credit to his quality."

Messi scored in the 35th minute in Argentina's 2-1 victory in the round of 16 fixture, a result which ended Australia's World Cup campaign.

The South Africa-born Baccus featured in all three games in Doha, coming from the bench twice before being entrusted with a starting midfield role against Argentina.

"It's a great feeling knowing that playing against the best in the world you can do well," he said, adding he felt no pre-game nerves.

"It's football, I have been playing football since I was four or five and have always loved it.

"I just go out there and do what I have been doing, love the game ... have fun, enjoy it."