gillen was born in kearny, new jersey and grew up in toms river, new jersey. gillen began playing soccer when he was four years old. at the time, his older brother was playing and after watching him play, gillen insisted on also playing. he attended toms river high school east winning the 1985 new jersey group iv high school soccer championship. gillen then attended pennsylvania state university where he played as a left back on the men’s soccer team from 1986 to 1989. gillen graduated with a bachelor’s degree in business. in july 1990, the cleveland crunch of major soccer league selected gillen with the tenth pick of that year’s draft. however, he decided against signing with the crunch and instead became an assistant coach with penn state before attending james madison university. he graduated from jmu with an mba.