Keegan Rosenberry didn't back down from a single challenge as a rookie in 2016. He played every second of every game for the Union, was named to the MLS All-Star team, and provided a spark on the backline that helped Philadelphia reach the MLS Cup Playoffs for the first time since 2011.

His early success is just a taste of what's ahead for the young defenders, and his teammates are convinced the his best play is still ahead of him.