The 17-year-old feels Newcastle have proven themselves against the big sides already this season.
And the 17-year-old insists the Magpies must 'go for it' when they come up against Jose Mourinho's side.
“There’s a lot of history at Stamford Bridge but we’ve got to keep working hard in training every day and go for it,” the Newcastle youngster told the Shields Gazette.
“Chelsea came to St James’s Park and we were the underdogs, but I thought we had our best game and won 2-1.
“Man City is a massive club with a huge stadium but we went there and won 2-0.”
Manager-less Newcastle are hardly in great form, of course but the Magpies are certainly capable of competing on a one-off big occasion, as Armstrong is alluding to.
Chelsea, meanwhile, have not won in two Premier League games but have a 100 per cent league record at Stamford Bridge this term.