Ryan Nelsen believes West Ham have issued a statement of intent by tying Winston Reid to a new deal.
Tottenham are keen for striker Shaquile Coulthirst to continue his development out on loan after his spell at Southend.
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."