If you were in any doubt about the magnitude of Saturday's Rugby World Cup Pool B meeting of Ireland and South Africa in Paris, Tuesday evening's Springbok squad announcement was a blunt reminder of what Andy Farrell's side will be facing this weekend.

There's always been an element of the mad scientists around Rassie Erasmus and Jacques Nienaber in their working relationship, who time and time again have chosen to zag when others have zigged.

Nothing about them has been predictable in recent months; the call-up of Jean Kleyn in June has proven to be a major success, their 33-man World Cup squad contained just two specialist hookers, and four scrum-halves, and when one of those hookers went down injured they replaced him with an out-half.

In the most high-profile of the experiments, the Springbok coaches have thrown an extra stick of dynamite into their 'Bomb Squad', with seven forwards and just one back among their replacements in the matchday 23 Stade de France on Saturday.

It was first rolled out for their 35-7 win against New Zealand late last month when a late injury to Willie le Roux saw them throw Kwagga Smith onto the bench in his place, and the performative act of bringing all seven of those forwards on in one go on 47 minutes just highlighted the novelty of what we were seeing.

South Africa destroyed New Zealand in their final warm-up game

It wasn't universally popular, with a minority of observers on this island feeling Erasmus and Nienaber were colouring outside the lines when it came to 'Rugby Values', while others claimed it was simply unsafe. For the vast majority of fans and pundits it was just another example of these coaches doing what they do best: innovating and challenging what we expect from the game.

The 35-3 win against the All Blacks stands up for itself, and so the 7:1 bench split was put into the back pocket of the coaches, and pulled out for this weekend's meeting with Ireland. Indeed, Nienaber explained that the concept was drawn up with games like this in mind.

"We analysed Ireland and after looking at them and what they bring and what we think we will need in this specific game from a tactical point of view and trying to counter everything they do - that's the reason we went with 7:1," he said yesterday.

With Ireland not announcing their team until Thursday lunchtime, the fact that South Africa have laid their cards down on the table so early adds another layer of intrigue to the week.

The game is meant to be fun, and picking apart the merits and risks involved in the South African strategy is just that.

The likelihood is that Andy Farrell's squad for this week was picked internally several days ago and relayed to the players before the Springbok announcement yesterday, but if the South Africans' early reveal creates even the slightest of doubts in the minds of the Irish players and management it will have achieved something.

When Farrell (above) does confirm his matchday 23 on Thursday afternoon, it will be fascinating to see whether or not he picks a side to play to their own strengths, or to neutralise the strengths of the Boks.

In the starting XV he has to decide whether or not to play Tadhg Beirne in the second or back row. Against Romania the Munster man started at blindside flanker with Joe McCarthy alongside James Ryan at lock, which allowed Ireland to effectively have an extra second row on the pitch and provide some extra size and weight in the pack.

Going with that selection would likely result in one of Josh van der Flier or Peter O'Mahony going to the bench. In that case, O'Mahony's lineout ability may tip the scales in his favour. The opportunity cost? World Player of the Year Josh van der Flier starts on the bench.

The alternative option is to stick with the familiarity of Ireland's traditional back five, keeping Beirne in the second row with O'Mahony, Van der Flier and Doris in the back row.

The temptation is there for Farrell to respond to the South African selection by choosing a 6:2 ratio of forwards to backs, but doing so would be a significant departure from the norm.

While the 6:2 bench split has been in vogue in recent years, it's not something Farrell has ever leaned towards, with all 44 of his games in charge to date seeing Ireland pick the traditional five forwards and three backs.

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Those railing against South Africa's jumped-up bench are ignoring the inherent risks that come with it and, since we've only seen it used once, overstating its effectiveness. While the sight of seven brutish forwards jogging onto the pitch in unison was enough to stop us in our tracks, the starters had done the real damage to the All Blacks by that stage, building up a 21-0 lead. In the 33 minutes that the seven replacement forwards were on the pitch for, South Africa outscored New Zealand by a reasonable, but not mind-blowing, 14-7.

Crucially, in picking a seven-man 'Bomb Squad', there's also the risk that it blows up in their faces.

With scrum-half Cobus Reinach as the only regular back, Erasmus and Nienaber have had to map out every eventuality to ensure they have adequate cover in case of injuries. Kwagga Smith, as the extra forward, can put his past Sevens experiences to good use if needed as an auxiliary centre or wing.

Were Ireland to choose just two backs on their replacements bench, they would be leaving too much to chance. You only have to go back to their last meeting with the Boks in November of last year for an example, when they lost both Conor Murray and Stuart McCloskey to injury in the opening half.

Ireland don't have a Kwagga Smith or a Sekou Macalou of France - who is as comfortable on the wing as he is on the side of a scrum - and so they need to stick to what they know.

Ireland, like South Africa, have to try and make sure the numbers add up.

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Watch live coverage of Ireland v South Africa (Saturday, 8pm) on RTÉ2 and RTÉ Player, listen to live commentary on RTÉ Radio 1, and follow live updates on RTÉ Sport Online and the RTÉ News app.