[3] On January 15, 2015, Shelton was selected 2nd overall by New York City FC in the 2015 MLS SuperDraft,[4][5] with the expansion club turning down an offer of a considerable amount of allocation money in exchange for their pick to instead draft the player who Head Coach Jason Kreis described as "our top guy".

[6] He made his debut for the club coming in their first Major League Soccer match, away to fellow expansion team Orlando City SC at the Citrus Bowl; he came on as a 62nd-minute substitute for Mehdi Ballouchy in an eventual 1–1 draw.

[7] Shelton totalled 17 games in his first season as his team missed out on the MLS Cup Playoffs, and scored one goal: on May 15 at Yankee Stadium against the Chicago Fire, he replaced Patrick Mullins after 60 minutes, and in added time he equalized for a 2–2 draw from David Villa's pass.

[11] Shelton was called up to the United States under-18 team in 2010, attending a training camp with them in California before flying out to Israel in December 2010 to compete in an international tournament against the hosts plus France and Germany.

[12][13][14] Some five years later, his drafting by New York City FC led to Shelton receiving a call-up to the United States under-23 in their games against Bosnia and Herzegovina and Denmark in March 2015.