However, it is expected that he will join Championship rivals West Bromwich Albion, with the Foxes expected to demand a considerable transfer fee.
It is believed that Mattock, who has made a total of 70 appearances for the club, handed in a transfer request at the beginning of last season. However, he decided to stay at the Walkers Stadium and help the Foxes win the League One title.
Pearson, despite showing frustration at his Left Back's decision, has enough cover at the left back position for Mattock's potential departure to lack any long term damage to the Foxes Championship prospects.