Personally, I was stunned when Buck Showalter, then a manager without a GM, snagged Darren O'Day off of waivers in November of 2011. Yes, he was coming off of a season in which he was injured (only pitching 16.2 innings) and ineffective (giving up seven home runs in that limited time). But O'Day's peripherals, outside of that garish home run rate, were still great: striking out over a batter per inning and walking fewer than one every three innings. Stats aren't the whole story, though, and the Rangers believed they had a deep enough bullpen that O'Day's struggles put him on the periphery. Still, letting go of a reliever with an unusual release point, funky delivery, and good peripherals was a risk.
The move worked out tremendously well for the Orioles, as while Jim Johnson compiled fifty-one saves and Pedro Strop blew hitters away in an outstanding first half, O'Day baffled opponents with his submariner ways and quietly became Showalter's fireman, only coming into the spotlight when Buck used him for seven innings in the Orioles' six playoff games. (Totals? One hit, one walk, and five strikeouts.)
The deal that O'Day was rewarded with (2 years, $5.8 million, with a club option for 2015) looked to be a fair one, with potential to be a steal for the O's if the reliever could stay healthy. With the guaranteed portion of the contract half-over, it still looks quite good for the Warehouse. O'Day regressed slightly in pretty much every category: strikeouts (9.27 -> 8.56 K/9 IP), walks (1.88 -> 2.18 BB/9), home runs (0.81 -> 1.02 HR/9), and thus FIP (2.96 -> 3.58), but despite being worse than last year, those are pretty good numbers. O'Day also pitched fewer innings (67 -> 62) due to some lingering soreness in his fingers, which made him day-to-day and unused for most of early September.
O'Day's struggles this year were in facing lefties, which is atypical for him, as he's been only a little less effective against lefties than righties over his career. Where he has struggled, though, is with the long ball, surrendering home runs to righties at a very low rate (0.54 HR/9 career) but at a high rate to lefties (1.49 HR/9 career). 2013 did a lot to bring up the latter number, as O'Day gave up five homers in twenty innings against left-handed hitters (2.25 HR/9). That's slightly worrying, as the last thing the Orioles need is another reliever who's only reliable against same-handed hitters, but there's reason to expect O'Day to be better against lefties next year, since they had a very high (i.e., lucky) HR/FB rate of 20%. (The league average is around 10%, and O'Day's career average, though not very predictive, is 14.4%.)
All that said, barring any health issues, Baltimore should expect more of the same from O'Day in 2014: ~65 innings of above-average, high-leverage relief work. He certainly has the potential to be elite again, and he was death on righties last year as usual (2.57 FIP), but even a merely above-average reliever making $3.2 million is good (though not great) value. That, and O'Day's just plain fun to watch.