A prolonged 2012 Super competition, with four mid-year Tests wedged in the middle, and a heavier travel burden in the new four-team Rugby Championship will test Wallabies like never before.

The jam-packed schedule could mean Australia’s leading stars play a maximum 36 matches – three more than what Wallabies ironman Will Genia gallantly soldiered through a World Cup-boosted 2011.

“This is the most difficult season for a Wallaby that I’ve seen,” said Queensland Reds coach McKenzie.

“You look at the calendar and it’s tough, really tough.”

For the first time, the new June international window will put a halt to the Super Rugby season for four weeks as the Wallabies immediately play a mid-week Test against Scotland before a three-match series against Wales.

Test players will then return to their Super franchises for the final three rounds of the competition before a three-week play-off series starts on July 20.

The rebadged Tri Nations, the Rugby Championship, which now also features Argentina, will kick off with the Wallabies playing the All Blacks on August 18 – a fortnight after the Super final.

With a third Bledisloe Test and the regular spring tour in Europe to follow, key Wallabies like Genia, ball scavenger David Pocock, backline star James O’Connor and captain James Horwill must be braced for a gruelling workload.

Former prop McKenzie, who started his 51-Test career in 1990 before the game went professional, stressed it would be impossible for the leading lights to play at top capacity throughout a 10-month playing season.

“It’s not going to happen,” he said. “You have to manage the players in that space.

“They will tell you they are willing but in the end they can only front so many times.”

Resting and rotation is set to become more of a norm at the Reds and the NSW Waratahs, where more than two-thirds of Robbie Deans’ Test players are based.

Queensland and the Waratahs are better than even-money bets to make the play-offs while the Western Force, Brumbies and Melbourne Rebels are rank outsiders.

McKenzie, who sees squad depth as more crucial than ever to success, believes the mental toll will be bigger than the physical for the Test stars.

“The biggest problem is going to be managing your Wallabies coming back when they’re coming off four Test matches (in June) and it’s mentally draining,” he said.

“The Wallabies are playing hard game after hard game so the capacity to integrate those guys back and freshen them up mentally (will be difficult).”

McKenzie’s experience coaching with Paris-based Stade Francais during Europe’s Six Nations has shown him how internationals also struggle to keep their focus on the premiership rugby.