World Series MVP Stephen Strasburg is opting out of his contract with the Washington Nationals, sources familiar with the situation tell ESPN's Jeff Passan.

Strasburg had four years and $100 million left on a deal he signed in 2016. He faced a Saturday deadline to opt out.

The 31-year-old enters free agency fresh off a regular season in which he posted a career-high 18 wins and led the National League with 209 innings pitched -- no small measure for a pitcher who has battled injury throughout his career.

He continued rolling in the playoffs. He became the first pitcher in major league history to win five games in a single postseason without a loss, his 47 strikeouts were tied for the second-most ever in a single postseason (Curt Schilling had 56 in 2001), and he posted a 1.98 ERA in six appearances overall.

The right-hander won two games in the World Series, including a pivotal Game 6 in Houston in which he became the first starter to go at least eight innings in a World Series since Matt Harvey in Game 5 in 2015. The following night, Washington won Game 7 and Strasburg became the first No. 1 overall draft pick to be named World Series MVP.

Opting out doesn't mean Strasburg won't return to Washington, which drafted him out of San Diego State in 2009. But he'll at least test the free agent market, which will be highlighted pitching-wise by him and Gerrit Cole.

Strasburg, who is represented by Scott Boras, is a career 112-58 with a 3.17 ERA and 1,695 strikeouts over 1,428.2 innings.

Washington also must decide what to do with free-agent third baseman Anthony Rendon, who is a free agent after hitting 34 home runs, 44 doubles and a major league best 126 RBIs this past season.