Calm has returned to the streets of Pretoria following a chaotic march against immigrants on Friday..
The day got off to an explosive start with Chinese doubles specialist Peng Shuai upsetting fourth-seeded Agnieszka Radwanska of Poland 6-3 6-4 and finished under the floodlights in the early morning hours with Wawrinka losing his cool and snapping at the rowdy crowd before escaping with a testy win.
After cruising through the opening two sets, Wawrinka had appeared set for a routine victory but the Swiss suddenly found himself in a titanic struggle with both the 95th-ranked Brazilian and some spectators.
With the tension building and the score locked at 5-5 after the Swiss had broken back in the sixth game, Wawrinka's mumblings turned to open rage as he screamed at one heckler to "shut up man".
The Australian Open champion would, however, quickly regain his composure as the set moved to a tiebreak, which he dominated 7-1.
"I was trying to keep the focus you know when you drop your level against Bellucci, it is tough," Wawrinka said in a courtside interview. "He started to play better and it started to be a really tricky match."
By contrast, Peng, half of this year's French Open women's doubles winning pair, quietly went about her business, taking 96 minutes on a sun-baked Louis Armstrong Stadium court to claim the biggest scalp of the tournament so far.
Radwanska, winner of the Montreal hardcourt tune-up to the US Open and a semifinalist at this year's Australian Open, saved a match point in the ninth game to hold serve for 5-4 and fended off another in the next to briefly delay the upset.
"I had two match points and didn't make it," said Peng, who has 16 career doubles wins and in February became the first Chinese player to be ranked as a world number one in tennis."
Two former champions, fifth seed Maria Sharapova and 19th-seeded Venus Williams, delighted their centre court audiences by flashing a little of their fashion style along with some on-court flair.
Williams, who claimed back-to-back US Open titles from 2000, tamed 78th-ranked Timea Bacsinszky of Switzerland 6-1 6-4 to reach the third round for the first time in four years.
French Open champion Sharapova lost the first set to 95th-ranked Alexandra Dulgheru of Romania, but the five-time grand slam winner recovered to register a 4-6 6-3 6-2 win and leave her fans smiling on a breezy Arthur Ashe Stadium court.
In another women's singles encounter, world number two Simona Halep of Romania beat the heat by hurrying past Jana Cepelova of Slovakia 6-2 6-1.
Johanna Larsson of Sweden, ranked 96th, sent another seed packing with a 5-7 6-4 6-2 upset of 21st-seeded American Sloane Stephens.