That might be hard to believe, considering he placed second overall in the District 3 Class AAA Cross Country Championships in October.
"I think the first time I ran was the Turkey Trot when I was in seventh grade, and that was an awful experience," said the Dallastown junior. "The longest I ran before was the mile in gym class, and that was awful."
Reilly raced through the 3.1-mile Parkview course in 16:43 this year at districts, and earned a spot at the PIAA Class AAA cross country championships, where he placed 54th overall in 16:54 out of 219 total finishers.
At first, Reilly said he saw himself as a baseball player, rather than a runner.
"I first took up cross country in eighth grade, and that was because I played baseball my whole life, and I just wanted to try a new sport," Reilly said.
But he has some support at home. Reilly's mother is also a runner, he said.
"She does a lot of local races. She definitely supported me when I started. My goal used to be to keep up with Mom," Reilly said.
Now even Reilly's mother might be struggling to keep up with him. Other cross country runners in the YAIAA certainly are.
Reilly broke the South Western course record this year at a regular-season meet on Oct. 2. He won the meet in 16:41, seven seconds ahead of South Western's Ryan Hertzog.
"I guess (running) just leaves you with a good sense of accomplishment," Reilly said. "You can always set goals and try to achieve those goals."
When he's not breaking records or racing for titles, here's a look at what the Division I boys' Runner of the Year has his mind set on in the offseason:
Who's your role model?
I looked up to Adam Katora. He was our number one guy. This year I tried to model some of the things he did last year, and he was successful.
What's on your iPod when you run? What music do you like to listen to?
I listen to a mix. I either listen to rock or hip-hop, depending on what mood I'm in.
Did you vote in this year's election? What was it like?
I didn't really put too much thought into the election. (Reilly turned 17 on Dec. 5.) I guess I should start worrying about that because I can soon vote. It would have been nice to vote.
What do you want to be when you grow up?
I'm thinking of maybe doing pre-med in college and maybe becoming a doctor.
In school I always had an interest in science and math.
I enjoy school; I put a lot of work into it.
Do you have a favorite subject in school?
Who's your favorite teacher?
I guess I have to say Mr. Noll, because he's my cross country coach (and history teacher).
What's your favorite time of year?
I'd say I like either the spring or fall. Summer and winter are the extremes.
What's your favorite thing to do on a cold or dreary day?
I actually still like to run in the cold. Other than that, I guess just watch TV or watch football. (Reilly is a fan of the Baltimore Ravens)
What other sports do you like?
I'd say running's my main sport, but I still play baseball in the spring after track season ends.
Who are your favorite baseball team and player?
I like Adam Jones on the Orioles. I don't know. He's a good player and a good sportsman, and he's fun to watch.
Do you have any pets? What kind and what are their names?
I have two cats (Carl and Molly), a dog (Lacy, a Shih Tzu), and a ball python.
If you could travel to anywhere in the world, where would you go?
I'd like to go somewhere in Europe, maybe see London or Spain.
In Spanish class we learn a lot about Spain and the culture there. It seems really interesting.