The Boks are blessed with a blur of wingers. Hotsteppers Cheslin Kolbe and Kurt-Lee Arendse appear to be the front-runners, but Ethan Hooker and Canan Moodie are not far off, not to mention the uncapped Jaco Williams. This is before mentioning versatile players that can cover wing like Aphelele Fassi and the electric Grant Williams.
As such, when you get that opportunity to pull on the green and gold, you best be outstanding. And van der Merwe - who is part of the unofficial Scrum Cap Mafia - has done just that.
The 30-year-old has five tries in five matches for the Boks. And just two weeks ago, he ran in a hat-trick of scores in the unofficial Test against the Barbarians in sunny Gqeberha. But a humble van der Merwe insists it's the team first.
"The coaching team cultivates an environment where you know precisely where you fit in and what the plans are," he told the press this week.
"Everyone knows the team comes first, so if you aren't playing, there isn't really time to feel sorry for yourself. Rather, you focus on what you can do for the team and how you can help the guy who is playing.
"When your opportunity comes, you must grab it with both hands."
Speaking about the upcoming match, van der Merwe pointed out the familiarity he has with many of the Scotland players, in particular, those with very un-Scottish surnames such as Schoeman and Steyn.
While SA-born prop Pierre Schoeman will be delving in the dark arts at scrumtime, far away from van der Merwe, winger Kyle Steyn will be charging right at him.
"Our advantage is that we play in the URC regularly against the Scots who will be playing this weekend," he continued.
"I've played a few times against the wings who could possibly play. The coaching staff also have excellent profiles on the opposition players, so we know precisely what is coming.
"We [referring to Steyn] played together at Stellenbosch University, so we've known each other for quite some time. It will be good to play against him this weekend."
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