Diamond is an academy product at Sunderland and has spent two of the last three seasons on loan with Harrogate Town, furthering his development.
While he has played for Sunderland in between the two loan spells, he has taken to the pitch more times for Harrogate.
The League Two side want him back and this time they are looking to sign him on a permanent basis.
However, they have competition on their hands as League One side Fleetwood have now joined the race to sign the Sunderland winger.
Fleetwood are hoping to improve on their struggles last time out, when they flirted with relegation, under new head coach Scott Brown and see Diamond as a suitable addition to the squad.
It remains to be seen who emerges on top to sign the young Sunderland winger and if the allure of League One football with Fleetwood becomes tempting to Diamond.
Last season, Diamond made 39 appearances for Harrogate in League Two and registered 13 goals along with six assists.
