With fellow right-back Nathaniel Clyne sidelined by injury, Alexander-Arnold could come into the team at Vicarage Road for what would be only his third Premier League start.
The 18-year-old Liverpudlian, quoted by a number of national newspapers, said: "I'm not sure whether I will get that opportunity but I am hoping to take it if I do get it.
"I will be fighting for that position, as will all the other lads. There are a lot of strong players here and we could put two different teams out at the start of the season.
"But hopefully the chance comes. You just hope for the opportunity. If I do get told I am playing against Watford I will look to take that chance."
Alexander-Arnold recently impressed in a 3-0 friendly victory against Bayern Munich that saw him go up against former France winger Franck Ribery.
The teenager says he makes a point of trying not to be overawed by such tasks.
"I try not to pay too much respect to the players I am playing against," the Liverpool academy graduate said.
"I think that is what can affect you. You have to go out there and focus on yourself and not who you are up against."