NEW YORK – NBA G League referees John Butler, Nate Green and Evan Scott have been promoted to full-time NBA staff officials, it was announced today by Monty McCutchen, NBA Vice President, Head of Referee Development and Training.

“John, Nate and Evan have achieved their promotions through the quality of their officiating being at the standard for working NBA games on a regular basis,” said McCutchen. “Our NBA G League is a great tool for officials to earn the right to rise to the NBA ranks and then continue to grow at their craft.”

In addition to their NBA assignments this season, the three new staff officials will continue to officiate NBA G League games. All NBA referees with fewer than four years of service in the NBA work NBA G League games to gain additional experience as crew chiefs and develop as leaders.

New Full-Time NBA Staff Officials

John Butler (Biloxi, Miss.) has officiated five seasons in the NBA G League and two seasons in the WNBA. He worked the NBA G League playoffs from 2015-19 and the Finals in 2018 and 2019. Butler officiated nine NBA regular-season games as a non-staff official during the 2018-19 season. He also has eight years of collegiate officiating experience. See his complete bio here.

Nate Green (Des Moines, Iowa) has worked four seasons as an NBA G League official. He officiated nine NBA regular-season games as a non-staff official during the 2018-19 season. Green also has six years of collegiate officiating experience. A standout player at Indiana State, Green was named the 1999-2000 Missouri Valley Player of the Year. He played professionally in the NBA G League (2001-03) and in Italy (2003-10). See his complete bio here.

Evan Scott (Taejon, South Korea) is one of four referees born outside the United States on the NBA officiating staff. He has officiated three seasons in the NBA G League. Scott worked nine NBA regular-season games as a non-staff official during the 2018-19 season. His officiating experience also includes five years in the collegiate ranks. Scott played two seasons of rugby at Radford University. See his complete bio here.

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Callahan Named G League Training and Development Lead

Mike Callahan, who retired as an NBA official following the 2018-19 campaign after having served on-court for 29 seasons, will join the NBA Referee Operations Department as G League Training and Development Lead, it was announced today by NBA President of League Operations, Byron Spruell.

In his new role, Callahan will be responsible for the implementation, development and execution of the G League referee educational curriculum. He will also oversee G League referee staff evaluation and development, including the transition of top candidates to the WNBA and NBA.

“We are thrilled that Mike will be bringing his vast experience and teaching abilities to our G League officials,” said Spruell. “He is the perfect mentor to develop our next generation of G League referees for on-court success and growth in their own officiating careers.”

Known as “Duke,” Callahan officiated 1,626 regular-season games and 225 playoff games, including 21 Finals games. He concluded his stellar NBA career as the crew chief for Game 4 of the 2019 NBA Finals.

George Tolliver, a former NBA official and member of NBA Referee Operations since 2004, will transition from G League Lead to Candidate Development Lead where he will oversee the strategic priority of implementing programs to identify new officials for the NBA’s developmental pipeline.