West Ham are in talks to sign midfielder Alex Song from Barcelona, according to Sky sources.
Jose Mourinho says Fernando Torres is part of his plans and that the striker has not told him he wants to leave.
Sky Bet Championship side Bolton announced on Monday they had signed the 22-year-old on a deal until January.
But Cardiff boss Malky Mackay then decided Mason should stay with the Barclays Premier League club and informed Wanderers counterpart Dougie Freedman later that evening.
A statement on Bolton's official website on Tuesday afternoon read: "Joe Mason will remain with Cardiff City following talks between Dougie Freedman and Cardiff boss Malky Mackay yesterday (Monday) evening.
"It was at the Cardiff manager's request that the striker remained in South Wales."