The local lad made his senior bow in the Europa League tie with Astana in Kazakhstan in November, 2019, which ensured he played in every age group from the age of nine to the first team.
Following a loan spell with Salford City, gaining valuable league experience, he returned to lead coach Neil Wood's group and captained the side towards the end of the season, while showing his potency and endeavour in attack.
"The end of my first chapter in football," Mellor posted on Instagram. "Making a debut for Man Utd is something that only a small number of people have the honour to say that they have achieved.