De Villiers: South Africa not guilty of ball tampering

"I know Faf very well," his former schoolmate told reporters.

"He is the last man on the field who will try anything like that," De Villiers insisted despite television pictures showing Du Plessis appearing to rub the ball on the zipper of his trouser pocket.

De Villiers said Du Plessis had been designated to look after the condition of the ball throughout the Pakistan innings.

"It is part of his responsibility to shine the ball, in order to get it swing, and look after it. It is not an easy job and I thought he did a very good job of it," De Villiers added.

But the umpires thought differently as South African captain Graeme Smith and Du Plessis were called over for a discussion with umpires Ian Gould and Rod Tucker.

The ball was then replaced from a box carried on to the pitch by fourth umpire Shozab Raza after which Gould signalled a five run-penalty, effectively accusing the top-ranked test side of unnaturally trying to alter the state of the ball.

"I don't even know where the message came from. There were no warnings, no talk of it. I still don't know the facts," said De Villiers.

The International Cricket Council have since confirmed the penalty, opening up the possibility that fines and possible suspension could be handed out.