Michael Cheika playing risky game by bringing only two hookers

Murphy's Law – "whatever can go wrong, will" – is something Australia coach Michael Cheika is unlikely to take too seriously.

While most teams will bring three scrumhalves and three hookers to the Rugby World Cup, the former Leinster boss will bring just two of each. How likely is Joe Schmidt to do likewise?

While Australia will turn to Matt Giteau if they run into trouble with Will Genia and Nick Phipps in the nine slot, Ireland don't have somebody of that ilk.

They do, however, have Ian Madigan. The livewire Leinster back has featured at scrumhalf before for his province, filling in ably during a sin-bin period against Connacht at the Sportsground.

The pass was zippy; his movement between rucks didn’t look particularly amiss. It should have made anybody who watched that little cameo sit up and wonder if Leinster and Ireland had been missing a trick all along.

Madigan will need to tick a few boxes – apart from passing from the base of the scrum, he’ll need to have worked on box-kicking, as well as knowing where the ball is coming from the lineout – but the tools are there.

In the same vein as Niall Quinn being Jack Charlton's emergency goalkeeper – those creative, innocent days before Fifa's bureaucrats insisted on naming three goalkeepers who can play at that position only – Schmidt should bring Madigan as his third nine.

Alongside Conor Murray and Eoin Reddan I'd bring Jonathan Sexton, Madigan and Paddy Jackson as the remaining halves.

The rest of the backs: Robbie Henshaw and Jared Payne with Rob Kearney, Luke Fitzgerald, Tommy Bowe, Simon Zebo, Keith Earls and the hopefully fit Andrew Trimble.

The bonus man, due to Madigan's extra role? Darren Cave as specialist centre cover, allowing Fitzgerald and Earls to concentrate on being wingers.

In the pack, hookers Best, Cronin and Strauss are straightfoward.

Questions over Marty Moore's fitness aside, it's all Leinster in the propping corps (Mike Ross, Moore, Cian Healy, Jack McGrath) with Michael Bent preparing for life on either side.

Paul O'Connell, Devin Toner, Iain Henderson and Donnacha Ryan fill the engine room.

Back row? Heaslip, O'Mahony, O'Brien, Chris Henry and Jordi Murphy with Henderson on double duty.

Schmidt is unlikely to copy Cheika’s other squad gambit: the pair of hookers. At first glance it looks an odd move, perhaps even reckless. But is it justifiable? And after murmurings of discontent from England, who jettisoned Dylan Hartley based on their understanding of the tournament regulations, is it legal?

World Rugby’s expansion of a match-day squad to 23, allowing for a direct replacement for each frontrow forward, brought with it some strict governance. It’s found in Law 3.5, and where hooking is concerned it boils down to this: a team must be able to field a replacement in the first instance of a substitute hooker being required such that scrums will continue to be contestable.

In the case of injury to a player at the World Cup, a replacement can be summoned. The conditions are that the replaced player cannot take further part in the tournament and the replacement cannot take the field for 48 hours. So what would happen if one of Australia's two hookers was injured in the warm-up?

While there must be six players in the match-day squad who can fulfill the three frontrow positions, they don’t have to divide neatly into three in the starting lineup and three on the bench.

An international match official said that in the scenario where Australia lost a hooker in the warm-up it would be up to Cheika to inform the referee of a late change to the team sheet and declare the replacement hooker, should one be required. The coach defines who's capable of playing hooker, and Cheika could name flanker David Pocock, for example, even though he's already likely to be in the team.

Even if Pocock could play the position adequately, a real issue would arise if he were to be carried off injured followed by the starting hooker being injured, sin-binned or sent off. Australia would find themselves with uncontested scrums and, crucially, forced down to 14 men for the duration that no declared hooker was available.

Cheika has played an optimistic hand; an awful lot of things need to go wrong for them to run into such trouble. But one of their hookers, Stephen Moore, is their captain. If injured early in week one, would he really be sent home immediately, necessitating a replacement at both hooker and captain? More concerning would the prospect of a semi-injured player being pressed into bench duty, and one solitary scrum, to avoid that man-loss penalty.

Whatever about Cheika’s lack of belief in that sacred principle set down by Murphy, he might also pay attention to Sullivan’s Law: “Murphy was an optimist.”