Size doesn't matter: The diminutive duo who are taking the Rugby World Cup by storm
South Africa's pocket rocket Faf is thriving in land of giants
A long time ago, while interviewing Mark McGurn at some launch or other, the ex-Ireland fitness coach had a theory.
McGurn proposed that as rugby players were getting bigger and bigger, the inevitable tactical innovation would see an added importance placed on having small, fast players in your team.
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For some reason, the thought stuck, and although much of the post-Shane Williams era has seen backs getting taller, wider and more powerful, the last couple of seasons has seen a pivot back to the pocket rockets having an influence on proceedings.
Less and less is rugby a game for all shapes and sizes, but in 5ft 7in duo Faf de Klerk and Cheslin Kolbe, South Africa have two diminutive stars who are crucial to their bid for tournament glory.
When they beat Ireland last weekend, Aaron Smith scored two tries and Sevu Reece caused havoc despite his small stature. Even Wales, who once boasted the heaviest backline in the business, have Gareth Davies bursting out of their defensive line and making game-winning plays.
Ireland's most effective attackers at this tournament were Andrew Conway and Jordan Larmour, two back-three players who punched well above their size and weight.
De Klerk has been one of the stars of this World Cup and yesterday he was asked about the number of small men making a big impact in Japan.
"It's great. I've had to do that my whole life, and I see guys coming through in our team. Cheslin (Kolbe) has been amazing for us, and for his club in France, where most people say you have to be big to play," he said.
"It gives a lot of young kids, and people who may shy away because of their size, confidence. If you are willing to work hard, you will reach your dreams. That's sometimes what I play for - to inspire younger kids and see what I can do. Hopefully, we can see a few more come through the ranks."
Since making his debut against Ireland in the three-Test series in 2016, De Klerk has become one of the Boks' most recognisable players.
Schooled in Pretoria, he earned that cap as a result of his form in Super Rugby for the Lions before making the move to Manchester in 2017.
Despite being based abroad, South Africa head coach Rassie Erasmus has made him a key leader in the side.
"The main thing for me when I got to Sale was I got put in a role where I needed to make a difference in the team. A lot of responsibility came my way in terms of how we want to play, how we want to kick, how we want to play our running game," he said.
"I started kicking for poles a lot more, started doing kick-offs. That all helped me a lot to get to where I am now. I played a lot of rugby, got a lot of starts. The head coach, Steve Diamond, backed me continuously.
"Playing with a lot less pressure and just enjoying yourself and getting into the groove again. Then, coming back into the South Africa squad with coach Rassie and everyone we worked with in 2016, it was just a similar thing - the coach backing the players and knowing what they can bring.
"It's then up to us as players to execute whatever they give to us, and we have to perform at the weekend."
De Klerk's try was the main moment from last Sunday's win against Japan, but it is his defence that gets team-mates going.
An intelligent operator, he is given licence to roam by the Boks' former Munster defence coach Jacques Nienaber and at one point he cleverly tracked a Japanese backline move from behind, picking the pocket of the attacker before he knew he was there.
Even when he's asked to front up in a man-on-man hit, the diminutive Sale Shark is not found wanting.
"It's a massive lift in terms of physical pressure that a player puts on the opposition," Francois Louw said of his team-mate.
"There is no doubt a big hit from any player gets guys excited. Firstly, it creates defensive momentum and forces the attack to take a few steps back to realign their process and a guy like Faf is really good at it.
"He picks his moments - he sort of drifts behind the line and then rabbits out to make big spot tackles, usually on the big forwards, which I've got to say is quite impressive from a little guy.
"He's got a big heart, and he's solid defensively. He's a great guy to have in your side."
In Sunday's semi-final against Wales, traditionally one of the biggest sides around, the smallest man on the field will be the key man.