Werth says at his introductory news conference Wednesday that the length of his seven-year, $126 million free-agent deal and assurances he received from ownership about a willingness to improve were key factors in his decision to join Washington.
His contract has a full no-trade clause.
Having come from NL East rival Philadelphia, Werth is familiar with the Nationals, who are coming off three consecutive last-place finishes. Nationals general manager Mike Rizzo says he explained to Werth "what our roadmap is to success" and told the right fielder "what we're going to do next week, next month, next year, three years from now and five years from now."