A late replacement and stylistic switch-up means that the challenge of Chad Mendes could arguably be a tougher one than that of original opponent Jose Aldo for Conor McGregor.
The bookies see
The Notorious as a 4/7 favourite over the Team Alpha Male standout but McGregor will undoubtedly face the sternest test of his seven-year fight career.
With a perfect UFC record of 5-0, McGregor has yet to face an obstacle that has come close to slowing his acscent to the top of the featherweight division but
Money will provide some intriguing questions for the Irishman and come Sunday morning, there will be no doubt as to who can pose the biggest threat to Jose Aldo's legacy as the best ever at 145lbs.
We've highlighted some of those key questions and supposed some strategies that the Dubliner can employ to go about answering them.
Weathering the early storm
With a combined 19 first round finishes between McGregor and Mendes, the lengthy build-up to UFC 189 could very well be realised with less than five minutes of action.
Mendes is not one to pace himself and the fact that he's coming in on three weeks notice for a five-round fight means that if it goes past the second round, it ought to be McGregor's to lose.
Against Nik Lentz, we saw Mendes come out winging punches in pursuit of an early shower and had Lentz in trouble after this combination connected in the first minute.
But Lentz gutted it out and lasted the distance which led to some cracks appearing in Mendes' game, particularly in terms of energy and output.
Just three minutes after that early onslaught, Mendes' aggression waned and he was taking noticeable breaks from the activity he showed at the beginning of the fight.
His speed and power dropped off considerably and, if McGregor's chin can withstand the first 120 seconds of
Money's attack then he should have the better gas tank.
Leg kicks
Back in the good old days of two weeks ago when it was McGregor v Aldo for the world title, much was made of the Brazilian's vicious leg kicks.
MMA pundits were advising Aldo to invest in the leg kicks early so as to hinder the dazzling movement of the Irishman later on.
And while Aldo certainly holds a power advantage in leg kicks, McGregor's new opponent is no stranger to that technique either and actually enjoys a significant edge in terms of volume of leg kicks thrown over their respective UFC careers.
Out of Aldo's significant strikes, he's targeted the legs 18% of the time since his first official UFC bout in 2011 while Mendes has been successful with leg kicks on 30% of occasions.
Mendes uses the inside leg kick, which isn't as powerful as the traditional outside leg kick, to wear on his opponents and we saw him land with it 12 times en route to a unanimous decision victory over Rani Yahya.
While he throws them often and volume can niggle away at the legs of fighters over the course of five rounds, Mendes lacks the technique necessary to do any real damage.
Against Yahya, we saw him lean back too much which took him off balance but he also put himself in serious danger by lowering his hands and failing to tuck his chin when throwing the kick.
Against a tall striker like McGregor who loves to throw straight punches down the pipe, Mendes could fathomably leave himself open to the left straight which is one of the Irishman's best weapons.
The way that McGregor places his feet when fighting also means it is easier for him to check the inside leg kick of Mendes.
McGregor holds his lead foot at an angle from his opponent in the way that a Taekwon-do practitioner does rather than the more common straight-ahead angle that's used in Muay Thai.
For inside leg kicks, that means McGregor must just lift his foot to protect his thigh instead of turning his leg and lifting the foot off the mat.
Level change
The wrestling game is another element of this fight that most believe is key for Mendes if he is to come away with the victory.
The Team Alpha Male fighter is probably the most decorated wrestler in the featherweight division and was an All-American wrestler in college.
Mendes is one of the faster level changers in the sport and it's far from inconceivable that he gets a hold of McGregor's hips and takes him for a ride.
The closest that we've come to seeing the Dubliner get taken down was against Dennis Siver when the German took advantage of an off-balance McGregor to just about take the fight to the ground, although neither was registered as an official takedown.
It wasn't the most trying task for McGregor to post and return to his feet but it quite simply won't be as easy against the relentless grind of a Mendes.
McGregor doesn't want to get into a grappling match with Mendes and ought to avoid standing straight on with his hips parallel to those of the American because that spells takedown.
The Notorious can keep the fight on the feet by maintaining his wide stance and keeping his hips as perpendicular as possible to Mendes.
In Mendes' first UFC bout he took down Michihiro Omigawa on each of his four attempts, all due to the fact that the Japanese fighter continued to keep a narrow base and stand straight-on to the American.
McGregor uses a wide stance better than anyone at 145lbs which means that the power double of Mendes is much trickier to complete.
We also saw the defensive wrestling skills of the Irishman on display when Diego Brandao got a tight bodylock on McGregor and attempted to drag him to the mat but
The Notorious showed explosive power by reversing the position.
Mendes' level change is so quick that he often uses it as a feint to get his opponent to change levels too which sets up an uppercut or right hook which was the beginning of the end for Ricardo Lamas in April.
Lazy top game
Let's say Mendes can manage to take McGregor down, what threats can he pose from top position?
Fortunately for the SBG fighter, the answer is "not a lot."
Mendes has a tendency to use his wrestling to set up rest periods in fights. He seldom threatens when he gets his opponents down but, rather, gets his breath back which can frustrate fans.
Against both Nik Lentz and Clay Guida, Mendes chose not to posture up and rain down punches but was content to just hold Guida in place to cement his place as round winner in the eyes of the judges.
But McGregor's Jiu-Jitsu is underrated. He's a brown belt under John Kavanagh and his long limbs will mean that he'll cause more trouble off his back than a Guida with submission attempts and sweeps.
We may not have seen much of McGregor's ground game because of his proclivity for the stand-up but he is much more of an output fighter on the mat than people give him credit for.
Utilisation of the rubber guard could be key and being the bigger, stronger athlete, McGregor should be able to elevate Mendes' hips to prevent this becoming a stalemate.
Keep the distance
McGregor performs at his best in a technical fight whereas Mendes, who could well be the hardest hitter at 145lbs, loves to stand in the pocket and trade.
With an eight inch reach advantage, McGregor should employ some Jon Jones tactics to keep Mendes on the outside.
That means keeping Mendes on the end of his jab, teeping if confident of his ability to defend a takedown and pawing with his lead hand.
When McGregor faced Diego Brandao, who has a similar frame to Mendes, he found his range early and Brandao couldn't get past the guard of the Irishman without sustaining damage.
McGregor used his lead hand like something of a fencing sword as he kept the Brazilian at bay before finishing him late in the first.
Avail of southpaw stance
Mendes' biggest weapon is unarguably his overhand right but that strike loses some of its effectivity against a southpaw due to the way that
Money disguises it.
Mendes likes to hide the counter overhand right behind the lead hand of his opponent which, to an orthodox fighter, is the left.
Against Yaotzin Meza, Mendes found himself in the perfect defensive range to avoid being hit by the jab of Meza (1). Mendes then feinted which caused his opponent to attempt a lead left hook (2). Mendes ducked under the hook and whipped his overhand right around it which left Meza unsighted (3). The fist came from behind Meza's shoulder and catches him flush on the chin.
The fact that McGregor will primarily fight from southpaw means that Mendes will have less of a surprise factor when it comes to throwing that strike because he will have no shoulder behind which he can hide the right hand.
This doesn't mean that McGregor can't get caught with it, he most certainly can. But he will have more visibility than an orthodox fighter which means that he'll have a greater response time.
Lateral movement
We reckon that we're going to hear these two words roared by John Kavanagh throughout the main event on Saturday.
Whether it's to avoid Mendes shooting on his legs or keeping himself away from Mendes' vicious right hand, McGregor should make sideways movement a priority.
Circling anti-clockwise reduces the risk of being knocked out and, as we've seen, a stationary target will be put on his back by
Money.
Luckily McGregor possesses some of the most unpredictable movement of anyone on the UFC roster and he will rely on that if he's to avoid getting clipped.
