The 18-year-old from Ballarat, taken at pick 20 in the most recent draft, has kicked nine goals in three games for the reserves.
Fagan confirmed his addition for Thursday's sold-out clash after captain's run on Wednesday, admitting he may have played with the teenager's emotions when confirming the news.
"He was so excited; I got him into the office yesterday and told him he was in a bit of trouble and he was actually a bit nervous when he walked in," the coach said.
"Probably out of all the boys I've told over the years, he was probably more emotional than anyone I've seen.
"It means a lot to him.
"He's only played three reserves games, he's kicked a lot of goals, his tackle pressure is fantastic, he's got a few different attributes we think, in time, will give the opposition some difficulty."
Oscar McInerney will also return from suspension for the 3-1 side against the Magpies, who have begun impressively under new coach and former Lions premiership player Craig McRae.
"They could easily be on the top of the ladder at the moment," Fagan said of the 2-2 side.
"The two games they've lost they've had more inside 50s and more shots than their opposition, they pushed Geelong all the way.
"They're a pretty experienced side … I'm not subscribing to the theory that they're a young side."