Originally due to contest a three-round exhibition against former Springbok Pieter Muller, Spencer instead took on replacement Dommiqus Biezanack after Muller withdrew with a leg injury.
It was just as well for the former SA rugby star, with Spencer demonstrating why he had been more than a handful during his career on the rugby field, showing impressive skill in the ring in this pre-fight appetiser.
Meanwhile, Boitshepo Mandawe narrowly outpointed Mthobisi Buthelezi in a South African welterweight title eliminator on the same bill.
Although the judges voted unanimously for the more consistent Mandawe, he at times found himself on the wrong end of a fusilade of stinging blows during 10 hectic rounds.
Former IBO bantamweight champion and current No 1 WBC challenger, Simpiwe Vetyeka began his eight-round fight against Klaas Mboyaner as though victory was a formality.
But the tearaway Mboyane had other ideas and his work-rate more than acounted for Vetyeka's subtlety and skill.
Implored by trainer Nick Durandt, the casual Vetyeka finally appeared to shed his complacency in the last three rounds.
Mboyane, however, weathered the comeback of his opponent and sealed the split decision with the only knockdown of the fight in the closing stages.
In other fights, Nkosinathi Tshinavhe outpointed Samson Ndlovu, Sbusiso Khumalo and Prince Ndlovu fought out a draw after all three judges had a 57-57 scoreline, and Oumpe Striven showed he was a prospect for the future while outpointing Ashton Whiteboy.