Houston argued for a $4.55 million salary in Tuesday's hearing before arbitrators Mark Burstein, Jeanne Wood and Allen Ponak.
Players lead 7-6 with decisions pending for McHugh and pitchers Marcus Stroman, Jake Odorizzi and Trevor Bauer. Six more hearings are scheduled, and 22 decisions would be the most since players won 14 of 24 cases in 1990.
Baltimore and pitcher Kevin Gausman agreed Tuesday to a $5.6 million, one-year deal, avoiding a hearing scheduled for Wednesday.
McHugh heads to spring training projected as a sixth starter behind a rotation with Justin Verlander, Dallas Keuchel, Gerrit Cole, Lance McCullers Jr. and Charlie Morton. The Astros could decide to trade McHugh.
The 30-year-old right-hander was 5-2 with a 3.55 ERA in 12 starts last season. He was on the disabled list with tendinitis in his pitching shoulder until July 22.
Astros closer Ken Giles won his case on Feb. 3 and will earn $4.6 million instead of the team's $4.2 million offer.