He has scored four tries, including a memorable hat-trick against the Dragons, while also making his Heineken Cup debut at full-back against Montauban last month.
Asked what he will be looking for from the Limerick youngster against Canada, Declan Kidney said: "Just Keith to keep doing what he has been doing. Keith has been working away now for two-and-a-half years.
"He's been in the limelight over the last few months showing very well, but then he has been doing that too at training over the last year and a bit.
"The reason for doing that is, you do enough training so that when you come out then you just back yourself not to have to do anything special on days like next Saturday and just to keep doing what he is doing."
Ireland's 9 to 15 for the Canadian Test is one of the youngest selected for some time, with Earls (21), Luke Fitzgerald (21), Rob Kearney (22) and Tommy Bowe (24) in with the elder statesmen Ronan O'Gara (31), Eoin Reddan (27) and Brian O'Driscoll (29).
Probed on whether he was tempted to have a little bit more protection on the wing, with the experienced Girvan Dempsey and Geordan Murphy pushing for selection, Kidney explained that the pair were in his thoughts.
"Well I think it's very difficult to protect in a Test match anyway. I think there was a big temptation to play Geordan (Murphy) and a big temptation to play Girvan (Dempsey) as well too.
"You have a number of guys who have been showing well at full-back over a period of time and what we are trying to do is build a panel.
"Sometimes building a panel means you don't always get to play guys in their favoured position or even their best positions. It's just a case of getting guys out on the pitch.
"I think it's fair to say that all of those temptations were there but I'm looking forward to seeing how these guys go on Saturday.
"It's all about getting opportunities and seizing them to the best of their ability," the Corkman added.
"You can't hand out caps just for any other reason other than guys deserving it and they've shown that at training and they've shown that in the matches they've played.
"I think the guys getting the chance are delighted, the guys missing out are disappointed, and if you have those two ingredients you have the makings of a good squad."
Kidney has been enthused by what he has seen of the uncapped Earls this season and in previous campaigns, when he coached the Moyross native at Munster.
"Keith looks like to be enjoying himself, he has a good few attributes but let's get him a game under his belt on Saturday and we start talking about that after Saturday," he said.
"He's shown he's come into the line a good few times, his lines of running have been good, the speed he has shown has been good, his kicking game has been good.
"Jeez, that's a lot of things...I'd better balance that out with a few other things!
"He's getting picked because he deserves to be picked and I'll try to not make it any harder for him by building it up more than that."