And for once, it involved a South African - maybe even two, if we claim Roger Federer.
Federer, 36, breezed through the opening set in just 26 minutes, had a match point in the third set and was just two points from victory a few times in the epic fifth set that lasted 90 minutes.
But Anderson had found his game, going unbroken on serve through the last three sets en route to his first Wimbledon semifinal.
Like Federer and Anderson, Nadal and del Potro Nadal slugged it out for more than four pulsating hours before Spain's 17-times major victor finally landed the knockout punch.
After missing out on a second-set tie-breaker, the 32-year-old from Johannesburg broke the Federer serve to win it 7-5, and the belief came blooding back.
Next, it was Nadal's turn to engage in a marathon match when he outlasted Del Potro on Centre Court. "Then you have moments in the match where you rise to the occasion and play very well".
Strokes of Genius is a world-class documentary capturing the historic 13-year rivalry between tennis icons Roger Federer and Rafael Nadal. After that I never really felt exactly 100 %.
"Of course this is an important result for me", Nadal said after the match. As the match went on, I gave it my all. Then in the 23rd game, at 11-all, 30-30 Federer blinked, sending down a double-fault and then drove a forehand into the net to allow his giant opponent to serve for a place in the semifinals.
"It was just one of those days where you hope to get by somehow", said Federer, who last played at No. 1 Court in 2015. I don't know if it had something to do with the breeze, just a bad day from my side, except the first set.
Despite leading by two sets and having a match point, Federer was beaten by South African big-server Anderson in the biggest shock of the tournament so far.
That took great self-belief, he added, knowing that he had never taken a set off 20-time major victor Federer in four previous meetings.
Six times Anderson was required to hold serve to stay alive and each time he was equal to the task.
That ended Federer's streak of consecutive sets won at the All England Club at 34, with the former world No 1 unable to break his own record.
"I was actually playing really high-quality tennis, having a few sniffs on his serve, nearly felt my mind wondering, Well, maybe I can do this".
"I like the level of tennis that I'm playing on right now". "I had my chances". That's my problem really, the 36-year-old said.
Del Potro, the 2009 US Open champion, is trying to reach the semi-finals for the second time, five years after losing to Djokovic in the longest last-four match ever played at the tournament.