Prior to the 2013–14 trade deadline, the Blues traded Halák, Chris Stewart, William Carrier, a first-round draft pick in 2015, and a conditional third-round draft pick in 2014 to the Buffalo Sabres in exchange for Ryan Miller and Steve Ott on 28 February 2014. Halák did not appear in a game for the Sabres and was ultimately dealt along with a third round draft pick to the Washington Capitals in exchange for Michal Neuvirth and Rostislav Klesla at the trade deadline. Halák dressed for the Sabres as the backup goaltender in one game, making him the 10th player in Sabres history to dress for the team in a regular-season game but not play.