Khulisu Mudau gave Sundowns the lead in the 67th minute, but it was canceled out just five minutes later by Mohamed Abdel-Rahman, who took advantage of a mistake by Williams and scored into an empty net.
However, Williams redeemed himself in the 90+2 minute by saving Athar El-Taher's spot-kick and preserving his team's unbeaten run in the group stage.
With the draw, the South African powerhouse lie top of the group with 11 points, one ahead of Al-Hilal of Sudan.
Meanwhile, the Egyptian giants Ahly remain third with 7 points and will need to win their final match against Al-Hilal to advance to the quarterfinals.
A tie in points between the Egyptian and the Sudanese sides will be decided first by their head-to-head record then by goal differebce followed by most goals scored, according to the tournament regulations.
Al-Hilal won the first leg in Sudan 1-0.
Both teams have the same goal difference (+3). However, Ahly have scored 11 goals and Al-Hilal netted six in all five games played in the group stage.
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