In addition to recalling Matusz on Friday, Baltimore also activated infielder Ryan Flaherty from the 15-day disabled list (tonsil infection). To make room on the 25-man roster, the O's designated lefty reliever J.C. Romero for assignment and optioned right-handed starter Tommy Hunter.
After going 5-10 with a 5.42 ERA in 16 Major League starts this season, Matusz went 2-1 with a 4.21 ERA in 10 games and six starts with Norfolk.
Romero, whom the O's acquired from the Indians on Aug. 13, gave up three earned runs in four innings over five appearances with Baltimore.
Hunter gave up eight runs in three innings Wednesday in his most recent start, a 12-3 loss to the Rangers. He has gone 0-4 in his past seven starts.