[MLS] Toronto FC's Zac Herold, who started for the USA at the 2009 Under-17 World Cup, has retired at the age of 17 after it was discovered he had a heart condition.

Herold is at risk of developing a potentially fatal irregular heart rhythm, or arrhythmia, because he suffers from the condition Hypertrophic cardiomyopathy (HCM).

Before Saturday's  game against New England, Toronto will honor Herold in a ceremonial coin toss at BMO Field.

"Early in preseason, we did medicals on all our players, and obviously our doctor, Ira Smith, was concerned with some of Zac's results," said TFC general manager Mo Johnston. "From there he then began a series of tests with a variety of doctors, in both Canada and the U.S. Zac's health was first and foremost in this process. Our hearts go out to Zac and his family; it's a very difficult situation. We felt it was the right thing to do by honoring him in front of our fans, and give them a chance to show their support."

Herold grew up in the Florida youth program that produced Jozy Altidore and attended the U.S. U-17 residency program in Bradenton, Fla.

He was one of two 2009 U-17s to be taken in the 2010 MLS SuperDraft.