The decision came down to Matusz or reliever Brad Bergesen, who has been valuable coming out of the bullpen. He's allowed one run in his last two appearances covering 7 1/3 innings.
Matusz is coming off a five-hit shutout of Lehigh Valley on Thursday. In his last three starts for Triple-A Norfolk, he's allowed four earned runs over 23 innings while also doing a better job of maintaining his velocity.
Matusz's fastball topped out at 91 mph against Lehigh Valley and was consistently at 88-89 mph. His stamina improved enough that he threw 105 pitches over nine innings.
The Orioles will have to make a corresponding move to clear room on the 25-man roster.
Matusz, who was 1-4 with an 8.77 ERA with the Orioles before being optioned to Norfolk, will report to Camden Yards tomorrow and fly with the team to Oakland.
Meanwhile, Felix Pie is leading off tonight for the Orioles. Josh Bell is starting at third base.
For the Orioles:
Felix Pie LF
J.J. Hardy SS
Nick Markakis RF
Adam Jones CF
Vladimir Guerrero DH
Matt Wieters C
Chris Davis 1B
Josh Bell 3B
Blake Davis 2B
Jeremy Guthrie RHP