Miller, a pending unrestricted free agent this summer, has a no-trade clause and can approve any deal the Sabres try to make.
It has been widely speculated that the Capitals are looking to include goalie Michael Neuvirth in a package for Miller, and would have to include their first-round pick in either this summer's NHL Draft or in 2015.
McPhee is also in the market for a top-four defenseman and could try to acquire a second- or third-line energy forward.
New York Islanders defenseman Andrew MacDonald has attracted plenty of interest from numerous clubs, including Washington.
Forward Martin Erat and defenseman Dmitry Orlov, along with Neuvirth, requested to be traded this season, and McPhee is still trying to accommodate them.
The Capitals currently sit one point back of the final wild card spot in the Eastern Conference, and three points behind the Philadelphia Flyers for third in the Metropolitan Division.