Wayne Ferreira was the last South African to reach the fourth round, and another win for Anderson will match Cliff Drysdale's feat as the last to reach the quarterfinals in 1967.
"Wayne is a great player to aspire (to) and try and reach some of his achievements he made," Anderson said. "He was a great player, and (I've) still obviously got a long way to go to match some of his other achievements. But being in the fourth round is great. A of lot people think clay is not a surface I enjoy playing on."
The 23rd-seeded Anderson has two career titles compared to Ferreira's 15. He'll next face Spanish clay-court expert David Ferrer, who's seeded fourth.
Their career record is 1-1, with both matches on hard courts. Ferrer is the better player on clay, having reached the semifinals at Roland Garros last year.
"He's definitely one of the best players in the world obviously, and on clay courts he can be even tougher," Anderson said. "I played a good match against him at Indian Wells this year, so I'll definitely look back at that match and see what I did well. Clay court is a little bit different."
Raonic had more aces than his opponent -- 16 compared to eight -- and also produced more winners -- 50 to 31. But the Canadian also made more unforced errors, 38 to 15, and had his serve broken three times.
"I just lacked execution and just struggled a little bit ... especially having a break up in that third. I shouldn't have let that slip," Raonic said. "He's been playing pretty well on clay and this year in general. He's been winning pretty much all the matches he should win."