The 32-year-old O'Day went 5-2 with four saves, and he ranked seventh among American League relievers with a career-best 1.70 ERA over 68 appearances. He was a critical part of the O's bullpen, allowing just 13 earned runs over 68 2/3 innings and will make $4.25 million next season.
Markakis, who will now become a free agent along with Hundley, had his $17.5 million option declined, but both sides remain hopeful that he can remain an Oriole. The longest-tenured active player on the club, Markakis will get a $2 million buyout per the terms of his contract.
Hundley, who had a $5 million club option, will not get a buyout. Both players now join the Orioles' list of free agents, which also includes Nelson Cruz, Andrew Miller, Delmon Young, Kelly Johnson, Johan Santana, Alexi Casilla and Joe Saunders.
Brittany Ghiroli is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.