Fletcher is on the crew for the Spain vs. Chile game. American Mark Geiger is the head referee.
Fletcher, 37, who is from St. Catharines, Ont., is the third Canadian to be selected to work as an official at a FIFA World Cup. He's been working with the three-person crew headed by Geiger since 2011.
"We've become like a little family," Fletcher said of the unit.
"You're expected to operate together, hang out together, live together so it comes in really handy when you actually like each other," he added.
Officials only find out 72 hours in advance which match they're assigned to. It's supposed to prevent any favouritism or outside influence over their calls.
FIFA authorities select the best officials to keep working as the tournament progresses and teams are eliminated.
"I literally believe this when I tell you I'm one decision away from being sent home … it's the biggest tournament there is for world football, so for us there's nowhere to hide," Fletcher said.
"So if for some reason I have an error that impacts the outcome of a match, there are 24 other very capable trios willing to step in and be retained for the next phase," he added.