|Full name||John Diffley|
|Date of birth||January 11, 1967|
|Place of birth||New City, New York, United States|
|Height||5 ft 9 in (1.75 m)|
|1989–1991||Atlanta Attack (indoor)|
|1994||North Jersey Imperials|
|1995||Long Island Rough Riders|
|1996||Tampa Bay Mutiny||13||(0)|
|1997||Kansas City Wizards||6||(0)|
|1998–1999||Staten Island Vipers||32||(0)|
|2003||New York Freedom||6||(0)|
|1997–2001||St. John's University (assistant)|
|2003||New York Freedom (assistant)|
|* Senior club appearances and goals counted for the domestic league only.
Youth and college
Diffley attended Albertus Magnus High School of Rockland, New York where he played on the soccer team from 1981 to 1984. He was a Parade High School All-American and was inducted into the Albertus Magnus Hall of Fame in 1998. In 1985, he entered American University. He spent four seasons as a midfielder with American. During Diffley's freshman year, American went to the NCAA title game where the Eagles fell to the University of California, Los Angeles in eight overtimes. Diffley graduated in 1989 with honors and was inducted into the Hall of Fame in 2006.
In 1989, Diffley began his professional career with the Albany Capitals of the American Soccer League (ASL). At the conclusion of the ASL season, Diffley signed with the expansion indoor team Atlanta Attack of the American Indoor Soccer Association (AISA). The Attack finished second in the league 1989-1990 standings and went to the playoff semi-finals before losing to the Dayton Dynamo. In the 1990 off-season, the AISA renamed itself the National Professional Soccer League (NPSL). The Attack again finished second in the standings, but fell to Dayton again in the first round of the playoffs. That summer, Diffley moved to the Penn-Jersey Spirit of the American Professional Soccer League (APSL). Diffley then decided to try a career in Europe. He signed with Dutch Second Division club HFC Haarlem and spent the 1992-1993 season in the Netherlands. In 1994, Diffley joined the North Jersey Imperials of USISL, where he was captain and was named to the USISL All-Star team. The next season, 1995, he signed with the Long Island Rough Riders. That year, Long Island won the USISL national championship. Diffley was named to the Championship All-Tournament team. The Tampa Bay Mutiny of Major League Soccer (MLS) drafted Diffley in the third round (twenty-seventh overall) of the 1996 Draft. He saw time in thirteen games before being traded to the Kansas City Wizards for the 1997 season. When the Wizards released him, Diffley became a full-time coach but continued to play for the Staten Island Vipers in 1998 and 1999. In 2003, Diffley was a player-assistant coach with the New York Freedom.
In 1995, Diffley became the head coach for the Dominican College men's soccer team. In 1997, he moved to St. John's University where he served as an assistant coach with the men's soccer team while working on his master's degree in business administration.
In 2001, Diffley gained his master's degree and left St. John's to work in the financial industry. On January 1, 2004, Diffley returned to St. John's when the school hired him as its Senior Associate Athletic Director for Administration.
Diffley earned seven caps with the U.S. national team in 1988. He earned his first cap as a substitute for Jeff Agoos in a 1-0 loss to Guatemala on January 10, 1988. Earned eight caps for the U.S. in 1988 when he contended for a spot on the U.S. Olympic Team. His last game came six months later as a substitute for Brian Bliss in a June 12 tie with Ecuador. At the time the national team was preparing for the 1988 Summer Olympics. Diffley was selected as an alternate for the 1988 for the U.S. Olympic Team.
American University inducted Diffley into its Athletic Hall of Fame in 2006.