Martin Maldonado has regressed at the plate in 2013, slashing .184/.253/.303 over 83 plate appearances.
In his first real exposure to Major League pitching, Maldonado batted .266/.321/.408 in 256 plate appearances last season. Perhaps he's toting his struggles onto the field with his catcher's gear. Maldonado has been a run worse than average defensively this year, according to Baseball Reference.
Antonio Bastardo has a 2.35 ERA through 19 appearances despite a mediocre 1.43 WHIP.
Bastardo has also blown two saves. He's punching out 4.6 less hitters per nine innings then he did last year, when he had a poor 4.33 ERA, and he's allowing more hits and walks. If Bastardo doesn't become more stingy with base runners, his peripherals will begin to wreak havoc on his ERA.
Over 19 relief appearances, Charlie Furbush owns a 4.42 ERA in 18 1/3 innings.
The 27-year-old lefthander established himself as a potential bullpen asset in 2012, posting a 2.72 ERA over 48 appearances. In 28 less innings this year, Furbush has given up the same amount of homers (three) and only six less walks (10).
Tyler Clippard hasn't allowed a run in May.
Clippard is seventh in the National League with eight holds. He's collected three wins in 2013 and posted a 2.50 ERA, 1.00 WHIP and 19/11 K/BB ratio over 19 appearances. The Yankee Clippard had a 6.33 ERA over six starts in the Bronx as a rookie in 2007. In the six years since, he owns a sparkling 2.83 ERA and 1.09 WHIP for the Nationals. It's time for a new nickname, though The National Clippard leaves plenty to be desired.
Joaquin Arias has been one of baseball's worst hitters, slashing .205/.262/.205 through 43 plate appearances.
The utility infielder, making $925,000 this season, batted .270/.304/.389 with a .693 OPS in 344 plate appearances last season. He can be ignored in NL-only formats.
Jason Frasor has tallied a 3.65 ERA through 17 appearances in his first season for the Rangers.
Signed to a one-year, $1.5 million contract in early January, Frasor has improved upon 2012's disappointing campaign for the Blue Jays, where he posted a rough 4.12 ERA and 1.47 WHIP across 43-plus innings of relief. Frasor owns a 13/5 K/BB ratio and 1.29 WHIP through 12 1/3 frames.
Jeremy Horst has not carried over his success from 2012, posting a 5.09 ERA and 1.58 WHIP over 17 2/3 innings.
Luckily for him, Philly's bullpen depth is poor. A lack of attractive alternative options will only save Horst's job for so long, however, if he keeps getting lit up at this rate. Horst posted a 1.74 ERA over 44 games in limited time the last two seasons, which is probably why the Phillies have given him as much rope as they have.
Adam Ottavino boasts a 2.01 ERA over 22 1/3 relief innings for the Rockies.
Ottavino has pitched exceedingly well as a swingman, posting a 24/5 K/BB rate and 1.12 WHIP in 14 appearances. As a 27-year-old, he appears likely to remain in the majors over the duration of an entire season for the first time in his career.