With Kurtley Beale deemed unready to make the starting XV following his return from dealing with alcohol-related problems - he is likely to be included on the bench - O'Connor will act as the Wallabies' chief playmaker.
The series opener at Suncorp Stadium will be only his second Test at fly-half and given he is unproven in the position Deans' faith in his ability to unpick the Lions defence has the potential to backfire spectacularly.
Quade Cooper has been overlooked by Deans, who announces his team in the early hours of Thursday morning, while the two other players capable of operating at 10 will picked elsewhere.
Berrick Barnes looks set to start at full-back while the inventive Christian Lealiifano has been earmarked for inside centre, where he appears to have been preferred to the more defensive Pat McCabe.
The remarkable career of Israel Folau will continue when he makes his Test debut on the right wing in his first season in professional rugby union.
The 24-year-old enjoyed a successful spell in league, winning seven caps for Australia and making five appearances for Queensland in the State of Origin, before switching to AFL and then union.
Having won his fitness battle with a knee injury, Digby Ioane will fill the left wing slot with Will Genia's unchallenged ownership of the number nine jersey completing the backline.
While the Wallabies have a full compliment of fit threequarters apart from Beale, they have encountered worse luck up front with David Pocock, George Smith, Scott Higginbotham, Sitaleki Timani and Tatafu Polota-Nau unavailable.
Debutant Ben Mowen and openside Michael Hooper will pack down either side of Wycliff Palu in the back row, while Kane Douglas will join skipper James Horwill in the second row.
Benn Robinson and Ben Alexander are the likely starting props, with Australia's most capped hooker Stephen Moore offering experience.
Saturday's showdown in Brisbane is being viewed as critical to the outcome of the series, with former South Africa coach Jake White even stating the Lions will "crumble" if they lose the first Test.
Hooper, however, is refusing to stake everything on events at the Suncorp Stadium, pointing out that history proves a team can bounce back from defeat.
"We want to win that first Test, but in saying that we lost the first Test in 2001 in Brisbane but ended up winning the series," he said.
"You have to expect the unexpected and roll with what's happening.
"The fact the Lions haven't won a series since 1997 definitely makes them more dangerous. The hunger's there. They'll be really fuming and ready to go."