Zullo was one of the surprise inclusions in Osieck's 23-man squad named on Tuesday for next month's friendlies against New Zealand (June 5) and Serbia (June 7).

And with regular left-back David Carney unavailable through injury the Socceroos boss said Zullo, who has been in strong form with Dutch club side Utrecht, would be given first shot in the position for the upcoming two matches.

The left-back spot has been somewhat of a troubled position for the Socceroos since the retirement of stalwart Scott Chipperfield following the 2010 World Cup.

While Carney has made the position his own with a number of eye-catching performances, there has been a lack of depth in that area.

Midfielder Matt McKay and central defender Jade North have both been forced to cover the position when Carney has been unavailable through injury.

But after watching Zullo develop at Utrecht on a recent scouting mission in Europe, Osieck has backed the 22-year-old as the man to challenge Carney for a spot on the left side of defence in the future.

"I think he has good potential ... I like him, he's very busy player on left flank," Osieck said of Zullo.

"He brings in a lot of pace and has an excellent passing and crossing technique."

"I was really impressed by him and after I left Europe and came back to Australia I was permanently on the internet and following his activities at the club."

"From that game on he was a constant member of the team and played all games for the full 90 minutes."

"That's a good indication to me that he seems to be on a good path after a long absence with injury."

"I can tell you I have brought him in to be the left-back."

Another of the surprise inclusions in the squad is that of Turkey-based attacker James Troisi.

Like Zullo, Osieck has kept an eye on the 22-year-old's progress since he left an impression on the coach during the training camp in Dusseldorf prior to the Germany friendly in March.

"He's definitely got something, some very individual stuff that I like," Osieck said of the Kayserispor attacker.

"I have a good relationship with people in Turkey still and I made some inquiries about his form and what I got was positive."

"It's a great opportunity for him to be part of our group and that's why I invited him."

With the 2014 World Cup qualifying campaign beginning in September, Osieck said these two friendlies would give him a good indication of the squad he would choose to start Australia's journey towards the finals in Brazil.