Over those two years, he is a combined 12-4 with an ERA of 2.23. During that time, he has averaged 8.9 strikeouts per every nine innings with just 2.0 walks.
But last season - when he went 5-3 with a 2.18 ERA - one area stood out on his stat sheet and that was his numbers against left-handed hitters.
In 2012 for the Orioles, lefty batters hit just .207 with an OPS of .664 against O'Day. Last year, they hit .309 with an OPS of .922. Over his career, those numbers are .250/.734.
So what the heck happened last season?
"I pride myself on being able to get a lefty out in between a couple righties," O'Day said the other day in the O's clubhouse. "Last year, the differing splits were more a result of me not being able to locate the main pitches I throw to lefties, which are backdoor sliders and sinkers. For weeks at a time, I couldn't locate it and guys were getting hits. I think the numbers will correct themselves and I'll go back to getting them out."
Along those lines, O'Day has added a changeup this spring training for further help against lefty hitters.
"It's going to help me. I've been working on it hard down here and throwing it more than I probably will in a game. I think it can help me quite a bit," O'Day said.
The 31-year-old former Florida Gator has been a mainstay in that O's bullpen, but this year we won't see O'Day and Jim Johnson together as they often were the past two seasons.
Many Orioles were close with Johnson, maybe none more than O'Day.
"This is my fourth team and I have seen the business side of baseball firsthand and maybe understand it more than other guys," O'Day said.
"But we lost a good teammate, good friend and leader in the clubhouse. So it's tough to lose a friend. You first say 'Why?' But there always seems to be a plan, so we'll see how it shakes out. He was a leader on and off the field, and someone will have to step up and fill that void."
The Orioles have come to learn how much they can count on O'Day. He held right-handed hitters to an average of .154 and OPS of .443 last year, and in his career those numbers are .199 and .559. Pretty impressive, and now he looks to resume putting up solid stats against lefty hitters again as well.
O'Day is a pretty solid leader in an O's clubhouse with several leader types. So what does he want out of the 2014 season?
"You mean besides winning the World Series?" he said. "For me, I just want to be consistent. I think consistency can be boring sometimes, but that is what a manger wants out of a bullpen and relievers. I want to do what I've been doing for the past couple of years."