The 20-year-old is now a bonafide first-team player after breaking into Ole Gunnar Solskjaer's squad last season.
But it wasn't always easy for Williams whilst coming up through the ranks at United.
"I went to The Cliff when I was seven and met everyone, some of them are even my closest mates now," Williams said when asked how he got started at the club.
"Some have stayed and some have gone but I'm still really close with them.
"From then on it's just been year by year, getting through each year and making sure I get a contract for each year and then obviously getting to be the player I am now.
"My dad took me to my first game at Old Trafford and I just fell in love with it. From then I was just a mad United fan. I wasn't really happy when I went to The Cliff because I was used to being in school and being the best player, but when I went there I wasn't one of the best players really! I was down there in the bottom group.
"Mason's always been there [as one of the best players]. James Garner he was up there as well. There are a few players who are not here as well now.
"I was jealous at the time because they were skilful and everything. I think that's why I went further back, because I was a striker but now I'm a defender."