The 31-year-old left-hander asked the three-person panel for a raise from $1,675,000 to $2.4 million during Tuesday's hearing, and Washington argued for $2.2 million.
A decision by Dan Brent, Robert Herzog and Jeanne Wood is expected Wednesday.
Blevins spent his first seven big league seasons with Oakland and was traded to Washington in December 2013 for minor league outfielder Billy Burns. Blevins went 2-3 with a 4.87 ERA and 66 strikeouts in 57 1-3 innings last season over 64 appearances.
Pitcher Vance Worley beat Pittsburgh in arbitration Tuesday and will earn a $2.45 million salary this year rather than the team's offer of $2 million. Owners have won three of five decisions, and 15 cases remain scheduled through Feb. 20.