Volbrecht, who trained Sanders for the first 14 years of the heavyweight champion's professional career, said on Sunday they had a shared a close relationship.
Sanders (46) was killed during a robbery at a restaurant in Brits, North West, on Saturday night.
"I took over as his trainer for his first professional fight [against King Kong Dyubele in April 1989]," Volbrecht said. "I flew to Cape Town, where Corrie stayed at the time, to watch the fight, and I brought him back with me [to Benoni] afterwards.
"He stayed with me and my family until he got married. He was like a son to me."
Volbrecht said he had been fortunate to train some of the country's most prized pugilists, including former IBF lightweight title holder Philip Holiday, and IBF and WBA super-featherweight champion Brian Mitchell, but he was closer to Sanders than any of the other fighters under his tutelage.
"Corrie was different because he stayed in my house," Volbrecht said. "We were much closer because I gave him daily advice. We had a very good relationship."
Sanders beat Ukrainian Wladimir Klitschko in a second-round technical knockout in Hannover, Germany, to win the WBO heavyweight title in March 2003. The following year he held Klitschko's older brother Vitali for eight rounds before the fight was stopped in Los Angeles, California.
He retired in February 2008, after 46 professional fights, with 42 wins (31 of them by knockout) and only four defeats.
"He was a brilliant all-round sportsman," Volbrecht said. "A lot of people assume, because he was a big guy, that he had a powerful punch, but he was not a powerful guy who picked up heavy weights.
"His hand speed and accuracy made him so effective.
"Muscle means nothing in boxing, and Corrie knew that. He understood the techniques of the sport."
Volbrecht said Sanders, a keen golfer, had hoped to turn professional and wanted to play on the Champions Tour after he turned 50. "It was his dream to play on the seniors tour as a professional golfer," Volbrecht said.
"He had another four years to wait, but he was a brilliant golfer because he hit the ball so far."
Volbrecht had been stunned to hear of Sanders' death on Sunday morning. "How does somebody walk into a restaurant while people are eating and just start shooting? It doesn't make any sense," he said.
"I can't believe it. It's so senseless, like something out of a wild west movie." – Sapa