The move marks Williams’s return to the position he held before being hired by the Nationals in 2013.
Williams was on the Diamondbacks’ original roster when the team began play in 1998. He played in Arizona until finishing his major league career in 2003, and holds the team’s single-season RBI record with 142 in 1999.
Williams was hired as the Diamondbacks’s first base coach in 2009, before moving over to third base in 2011.
The Nationals earned a 179–145 record with Williams at the helm. He was named the National League Manager of the Year in 2014 after leading his team to an NL East title. He was fired after Washington struggled in 2015, winning 83 games and failing to make the playoffs.
The Nationals hired Dusty Baker to replace Williams.