David Shelley Duncan (born September 29, 1979) is an American former professional baseball player.

Duncan played in Major League Baseball (MLB) for the New York Yankees, Cleveland Indians, and Tampa Bay Rays.

[4] Playing with the Tampa Yankees of the Florida State League in 2004, Duncan hit 19 home runs in 424 at bats.

In 2007, Duncan was a member of the International League All-Star Team, and was the Topps IL Player of the Month in May while playing for the Triple-A Scranton/Wilkes-Barre Yankees.

[5] While with the Yankees AAA team, Duncan had 25 home runs, second in the International League at the time he was called up, and hit .295 with a .577 slugging percentage in 336 at-bats.

[4] Duncan made his major league debut on July 20, 2007, as the designated hitter against the Tampa Bay Devil Rays, and recorded his first career hit and RBI.

[8] Duncan later hit his fourth Major League home run at Yankee Stadium on July 31, 2007, against the Chicago White Sox.

On January 7, 2015, Duncan was announced as the new manager for the Arizona Diamondbacks' Low-A affiliate, the Hillsboro Hops of the Northwest League.

[20] On February 6, 2017, Duncan was named the manager of the Diamondbacks' High-A affiliate, the Visalia Rawhide.

[citation needed] On November 26, 2018, Duncan was hired by the Toronto Blue Jays to be their Major League field coordinator.

[1] Duncan was hired to manage the Scranton/Wilkes-Barre RailRiders, the Triple-A affiliate for the New York Yankees, for the 2023 season.

A bench-clearing brawl ensued, after which Duncan and Rays right fielder Jonny Gomes were ejected, as were two of the Yankees' coaches, Bobby Meacham and Kevin Long.