The 31-year-old Bafana Bafana right-back was injured as the Brazilians overcame Marumo Gallants 2-0 at Loftus Versfeld on Wednesday.
Malibongwe Khoza opened the scoring after 21 minutes and Cassius Mailula sealed the result with his goal in the 67th minute.
Mudau was stretchered off in the 37th minute after a heavy collision and was replaced by Zuko Mdunyelwa.
Speaking after the game, Downs boss Miguel Cardoso revealed that the injury was quite ‘severe’.
“Unfortunately, it’s a very, very severe injury, yeah,” Cardoso on IOL.
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“Obviously for a player with his calibre, with his quality, [it’s] a big loss for South Africa, and for us especially.”
“I’m feeling really frustrated. No, he got injured outside of the pitch on that action. There was no contact. I thought it was the one in the middle, but no,” Cardoso added.
“He was here. We reviewed the action. It was not. This one was not from a tackle.
“There are accidents in F1, there are injuries in football. Yeah, it’s a big loss, but let’s hope the other ones rise for the challenge ahead.”