2013 Stats: 45 G, 1-4 W-L, 2.58 ERA, 38.1 IP, 34 H, 15 R, 11 ER, 1 HR, 16 BB, 41 K, 149 ERA+, 1.304 WHIP, 8.0 H/9, 0.2 HR/9, 3.8 BB/9, 9.6 K/9, 2.56 K/BB, 0.6 WAR
Steamer: 45 G, 3-2 W-L, 3.72 ERA, 3.64 FIP, 45 IP, 9.77 H/9, 4.96 BB/9, 0.68 HR/9, 0.1 WAR
Oliver: 67 G, 3-4 W-L, 4.03 ERA, 3.79 FIP, 65 IP, 9.03 H/9, 5.42 BB/9, 0.56 HR/9, 0.0 WAR
Your Philadelphia Phillies know from bullpen volatility. The club saw former closer Brad Lidge turn in one of the best relief seasons in history in 2008, followed by arguably the very worst a year later. A few years earlier, it rode the Rheal Cormier rollercoaster as the French-Canadian lefty posted ERA+ scores of 101, 74, 235, 127 and 75 over his five full seasons with the club. Most recently, the Phillies have gotten burned in the late innings bringing in veterans—see Chad Qualls, 2012, and Chad Durbin, 2013—and trusting the kids (you might have blocked it out, but both Philippe Aumont and J.C. Ramirez briefly held the setup job in 2013).
If there was any upside to the miserable 2013 season out in the bullpen, it was that a passel of young pitchers got significant seasoning that might set them up for success down the line. Most of them struggled: Aumont nearly washed out of the organization (though he seems to be off to a positive start this spring), and Ramirez was cut loose this winter. But a few—B.J. Rosenberg and Ethan Martin, once he was shifted to a relief role—flashed enough raw talent to offer hope for better performance to come. Lefty Jake Diekman was probably the best of them all, showing improved command of his high-90s fastball and sharp slider.
An object of fascination ever since former pitching coach Rich Dubee fell in love with him two springs ago, Diekman looks like a really devastating weapon against lefty hitters in particular. The 26 year old faced southpaw batters on 69 occasions in 2013. He retired the batter 54 times, 23 on strikeouts, and gave up nine singles and six walks. Not one resulted in an extra-base hit. For the year, lefties put up a .148/.221/.148 line against Diekman. The Phillies once had another lefty who flirted with triple digits on his fastball and was known as death on same-side batsmen. But Billy Wagner’s career triple-slash facing left-handed hitters was a comparatively bloated .189/.262/.257.
Diekman stands out in two other respects. One, he simply doesn’t give up home runs. Through his minor league career, he surrendered an average of 0.4 homers per nine innings pitched, and that’s improved further since reaching the majors: he’s allowed just two in 65.2 big-league innings thus far. Two, his strikeout propensity increased as the competition got better through his minor league career: Diekman struck out just 6.1 batters per nine in 2008, then boosted his K rate to 8.4 at low-A in 2009, 9.1 at Lakewood and Clearwater in 2010, 11.5 at AA Reading in 2011, and 12.5 in his half-season at Lehigh Valley in 2012 ("falling" to 11.1 in 30 innings back at the level last season).
The concern with Diekman, and what likely will keep him from reaching truly elite levels, is his tendency to lose the strike zone. He’s never had a full-season WHIP under 1.37, and it’s not because he gives up hits. Back at triple-A last year, he walked an eye-popping 7.2 batters per nine. This got sharply better with the Phillies, where he kept the free passes to 3.8/9, and it’s reasonable to expect that the bouts of wildness will become fewer and less debilitating as he continues to gain experience.
Diekman isn’t quite a lock to break camp with the team for the first time in his career, though it would be surprising—and disappointing—if he doesn’t make the final cut. Nor is his likely role entirely clear: he’s probably too good, and too young, to fill a pure situational lefty role, but he might not yet be as effective against righties (.281/.379/.390 career line) as you’d hope from a true setup man. My guess is that fellow lefty Antonio Bastardo starts the season in that role, but given that Bastardo is sort of a less extreme version of Diekman in every respect other than posterior size, it wouldn’t be a shock to see them swap duties at some point. Either way, the Phillies’ hopes for dramatic improvement in the bullpen rest in large part on Diekman’s left arm.