The youngster impressed whilst out on loan at Derby County last season, where he was also managed by current manager Frank Lampard, and scored Chelsea's opener in their 4-0 pre-season win against St. Patrick's Athletic at the weekend.
Chelsea announced the deal with a statement on their website, with director Marina Granovskaia saying: "Mason has come right the way through the Chelsea Academy and has always stood out as a fantastic talent and dedicated individual. We have monitored his development extremely closely while he has been out on loan and believe he is now ready to be a member of our squad competing at the top of the Premier League".
The player has signed a five-year deal at Stamford Bridge, keeping him with the Blues until 2024, and also spoke to Chelsea's website about his new contract: "It’s a massively proud moment for myself and my family. I joined this club at six years old and it was always my goal to play for the first team one day.
"I’m really looking forward to the coming season now and working hard to have an impact here at Chelsea. I’ve been at the club for a long time already and hopefully I’ll stay for a long time to come", the 20 year-old added.
July 15, 2019