Will D.C. United's Chris Durkin be the next breakout American teenager in MLS?

American soccer players rarely used to make professional breakthroughs at age 18, but the standard for what is considered a young pro is changing quickly.Christian Pulisic and Tyler Adams enjoyed professional debuts when they were 17, while Weston McKennie made his first Schalke appearance when he was 18. Now D.C. United midfielder and former U.S. Under-17 national team standout Chris Durkin is...