Smith made 142 in Australia's second innings 487-7 declared on Sunday after the star batsman's 144 bailed them out to 284 following a collapse to 122-8 in their first innings.
The decision, taken during a board meeting last week, follows a disastrous South African World Cup campaign in which the Proteas finished seventh of the 10 teams.
Paul Pogba said in June that he could seek a new challenge after three years at United, while his agent told 'The Times' last month that the 26-year-old intends to leave the club amid reports linking him to Juventus and Real Madrid.
Cyrus Christie, who came on as a substitute in the former Premier League side’s first match back in England’s second tier, took to Twitter after the game to call out the instigators.