Farrell's new-look defence can put Irish on the attack
South Africa series could hinge on former England man's influence
Under Joe Schmidt, Ireland's adaptability to their opponents has always been their strongest suit.
At their best, Schmidt's side have been able to identify the perceived weaknesses in the side facing them and ruthlessly exploit it.
While there are central tenets on which the side are built, the New Zealander has built enough variety into the game-plan to be able to change completely from week to week.
How he manages to adapt when facing the same opponent on three consecutive weekends will be fascinating to watch.
In Allister Coetzee, Schmidt is facing a new coach with no back catalogue of games with the Springboks, who have a few new faces in their squad.
So, Ireland are faced with a fresh challenge but you can be sure that since the Six Nations Schmidt will have pored over whatever footage he could find in order to find an advantage.
And, while he is taking charge of his 33rd Test match as Ireland coach, the former Leinster supremo has a new weapon at his disposal in defence coach Andy Farrell, who is in the coaching booth for the first time on Saturday.
Schmidt also has a template from 2014 that he can dust off and reshape. His Ireland side out-smarted Heyneke Meyer's team that day at the Aviva Stadium, and the locals have not forgotten that beating.
Repeating the trick away from home and without Johnny Sexton is a huge ask, but the squad have spoken this week about their belief that a win is within their grasp.
If they are to achieve it, then Farrell will have a big role to play.
The former England defence coach wasn't of a mind to reveal his grand plan when he met the media for the first time last week, but you can be sure that increasing Ireland's aggression in defence has been one of his priorities.
With both England and the Lions Farrell's key emphasis was around using the defence as a form of attack thanks to a line-speed that cut off an opponents' options and forced them into errors that led to opportunities.
The new man has conceded that he is building on solid foundations put in place by his predecessor Les Kiss, but he will have his own ideas on how to improve.
South Africa have a host of impressive ball-carriers and Ireland will hope to get to them before they can get rumbling, denying them momentum and stopping their off-loading threat.
They also have pace out wide and until now Ireland have been vulnerable to quick, wide ball.
Farrell could invite Conor Murray into the line to help with spacing and is likely to ask wingers Andrew Trimble and Keith Earls to make decisions around whether they should be in the back-field waiting for a kick or in the faces of their opposite numbers.
The tactic could leave Ireland vulnerable to a chip in behind, but Farrell is banking on the defensive line rushing up so quickly that the out-half won't have time.
Aggression and attitude will be required if Ireland are to succeed.
The 2014 template
In the aftermath of the 29-15 win over the Springboks at the Aviva Stadium in 2014, Schmidt described his team's performance as "superhuman".
That's the level of effort he'll require from his players once again this weekend, when he looks for them to put their bodies on the line.
That day in Dublin, South Africa owned the ball and dominated territory, but they were stalled by a combination of their own error-count, a heroic defensive effort and Ireland's dominant breakdown strategy.
Schmidt's men were helped by a dreadful performance from Springbok scrum-half Francois Hougaard, whose errors cost his side at vital moments.
Had JP Pietersen not scored a late consolation try, it would have been Ireland's largest winning margin and it is one of the main reasons why the tourists are being taken seriously this week.
Much has changed in the intervening 20 months, but there are elements of the game-plan that can be dusted off.
Time to bring the maul back
The 2014 win was arguably the high-point of Ireland's relationship with their maul and perhaps it is time to rekindle the flame.
In the subsequent Six Nations and the World Cup, Simon Easterby's pack moved away from one of their most devastating tactics.
Rules around the maul have changed for this Test series, meaning players must transfer the ball backwards rather than swim back while still in possession, but that should not stop Ireland from trying to get the ball down and drive.
Devin Toner's lineout proficiency is a key reason why he is almost certain to start and his ability to identify the right moment to maul will be important.
Don't expect Ireland to start playing like Connacht just yet, but the arrival of Farrell should allow Schmidt more time to construct his attack after showing signs of development during the Six Nations.
That doesn't mean he is set to abandon his attritional three-ruck rotation system, but supporters can look forward to the prospect of seeing forwards passing in order to create space for the backs.
While Paddy Jackson is inexperienced at international level, he has been playing close to the line all season for Ulster and Schmidt will ask him to keep doing it in order to bring others into the game and find spaces by holding defenders a la Sexton at his best.
The out-half has grown as a provincial leader this season and his ability to assert his authority on proceedings and identify South African weaknesses will be a major factor.
Ireland could well go into this game without a recognised openside, preferring a ball-carrying trio in their back-row, and that means others will need a big game at the breakdown.
If Ireland can slow down South African ball and force turnovers through Rory Best, Jamie Heaslip and others then they can frustrate their hosts.
That will plant doubt in Coetzee's side's mind, and it is up to Ireland to capitalise and drive their advantage home.