Things don't always go according to plan, but they have so far for the O's bullpen. Excluding Brian Matusz, who has yet to pitch three full innings, every reliever has an ERA of 3 or below. Every reliever not named T.J. McFarland (3.15) and Dylan Bundy (3.96) also has a FIP under 3. Britton, O'Day, and Mychal Givens have strikeout rates of at least 11.7 per nine innings, and Brad Brach has a K/9 of 9.4.
With a blend of short and long relievers at his disposal, Buck Showalter has done a masterful job of spreading around the work to make up for a starting rotation that rarely makes it through six innings. That doesn't mean every reliever has been used in the most favorable spot; obviously you can nitpick with some of the decisions in various situations. But that's nearly impossible to do for a bullpen that carries such a heavy burden and workload.
O'Day and Britton are almost always used in the eighth and ninth innings, respectively, which allows Showalter to deploy Brach and Givens to put out fires in the sixth and seventh innings. I've written a decent amount about Givens recently, but Brach merits more praise for what he's transformed into.
For MASNsports.com last season, I wrote about how Brach was talented enough to slide into O'Day's role, were he to leave in free agency. He didn't, of course, giving Showalter plenty of relief options to choose from this season.
Brach, who primarily throws four-seamers, splitters, and sliders, joined the Orioles in 2014 and immediately gained about 1.5 mph on his fastball (to 94.7). Last year it jumped to 95.3, and so far this year he's up to 95.5. He's also thrown his slider harder every season since, along with throwing many more splitters. As Ryan Romano wrote early last season, Brach has taken full advantage of the increased velocity and nasty horizontal movement of his splitter, as it's become a legitimate weapon. Opposing batters had a much more difficult time squaring up on Brach's splitter, and the same has held true early this season. He's also throwing the splitter even lower in the zone.
Another large reason for Brach's success is that he's not a liability against left-handed hitters. In his career, right-handed batters have a .297 wOBA against him, while lefties have a wOBA of .283. He gets more strikeouts against right-handers, but allows home runs about twice as often.
Looking at one year of data can be misleading, but after struggling a bit against lefties in 2014 (.334 wOBA), Brach excelled against them in 2015 (.238 wOBA) after adding more splitters to his repertoire. It's not surprising that he'd throw more splitters, as it generates more whiffs per swing by a wide margin.
Brach might not strike out 10 batters per nine innings again like he did last season, but if he keeps that number somewhere above nine, cuts down on his walks, and does a better job of keeping the ball in the ballpark, he'll be a more efficient and effective pitcher. And right now, that's exactly what he's doing.