In the final year of his contract, during the 2016–17 season, the Blues were unable to work out an extension with Shattenkirk as he approached free agency. On February 27, 2017, prior to the trade deadline, Shattenkirk was traded (alongside Pheonix Copley) to the Washington Capitals in exchange for Zach Sanford, Brad Malone, a 2017 first-round draft pick and a conditional second-round draft pick in 2019. Shattenkirk left the Blues having played in 425 games and collecting 258 points, placing fifth all-time amongst defensemen in franchise history.