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Jake Diekman Emerging As Reliable Bullpen Option

If you have been following baseball with any regularity over the last few years, you are familiar with Aroldis Chapman, a lefty reliever with the Cincinnati Reds. Since making his Major League debut in 2010, he has been one of the most formidable relievers in all of baseball this side of Craig Kimbrel. He utilizes a fastball in the upper 90’s and a slider in the mid 80’s, his bread and butter.

Obviously, Chapman is in a league of his own — nobody compares to him, not even Billy Wagner, one of the greatest left-handed relievers of all time. However, did you know that the Phillies have their own lefty reliever who makes use of a fastball in the high 90’s and a mid 80’s slider? His name is Jake Diekman, and he has emerged as one of the Phillies’ more reliable arms as the season has gone on.

Watch Diekman’s pitches in action.

8/21 fastball to Todd Helton:

8/19 slider to Yasiel Puig:

In Diekman’s young career thus far, he has been able to strike out hitters at a rate roughly equivalent to that of Antonio Bastardo. Since the start of 2012, Bastardo missed 30.7 percent of bats while Diekman missed an even 30 percent. Whether due to pitch sequencing or Diekman’s inexperience, Bastardo has had an eight percent better strikeout rate, showing the ability to finish at-bats.

Another nice feature of Diekman’s arsenal is that he induces a fair amount of ground balls: 52 percent last year and 47 percent this year, an aggregate rate of 50 percent, which ranks 60th out of 221 qualified relievers. Unfortunately, those grounders haven’t been friendly to him yet — a combination of solid contact and the Phillies’ rapidly-declining defense — as he has a career .345 batting average on balls in play.

Diekman’s biggest problem over the first 50 or so innings has been control, walking 13 percent of hitters thus far. Diekman’s ability to harness his control will dictate whether he becomes one of the litany of forgettable arms that have phased in and out of the bullpen over the years, or whether he becomes a mainstay. Billy Wagner walked eight percent of batters he faced; over the last two years, Chapman has walked eight and ten percent. It doesn’t matter how hard you throw or how deceiving you can be if you can’t reliably locate your pitches, just ask Carlos Marmol.

As the .gif with Puig above shows, Diekman can be tough on right-handed hitters, but they have for the most part been an issue for him, posting a .367 weighted on-base average compared to the .244 of lefties. They hit fewer ground balls, and more line drives and fly balls. Almost all of the success right-handers have had against Diekman has come on fastballs, posting a .394 wOBA against those compared to .307 on “soft” stuff.

He comes from the side, which is one reason why left-handers have found him so tough. Right-handed hitters haven’t been fooled by it.

In a year in which the Phillies’ bullpen has ranked among baseball’s worst and many of their younger pitchers have failed to live up to expectations, Diekman has been a pleasant surprise. He is just 26 years old and isn’t eligible for arbitration until 2016, meaning he will continue to be an affordable option in the back of the bullpen for years to come.