On August 3, 2009, Neftali Feliz made his major league debut against the Athletics, pitching two perfect innings with four punchouts. In those innings, he mowed down hitters with 23 fastballs that averaged 99.45 mph, 4 changeups that averaged 91.13 mph, and 3 sliders that averaged 82.43 mph. He would end his rookie season with a 1.74 ERA (2.48 FP), a 33.3 K%, and a 6.8 BB%. As a 21 year-old, he already looked like a bonafide bullpen ace for the Rangers.

Fast forward to the end of spring training in 2014. Feliz is 25 years old and in the prime ages of his baseball career. And he’s starting in AAA. With a fastball that is 91-93 mph. Rangers’ General Manager Jon Daniels said of him, “He’s healthy and his work ethic has been solid, but he needs some work and the best place to get him that is in Round Rock right now. I expect he’ll be back as soon as he’s ready to help us.” A team whose bullpen for opening day included Seth Rosin thought that Feliz wasn’t ready to contribute for them out of the gate. Clearly something was off.

On August 1, 2012, Neftali Feliz underwent Tommy John surgery. Tommy John surgery generally requires at least 12 months for recovery, and he was back in the majors by September 2013. He averaged 94.19 mph with his fastball during his 6 games in September 2013. While his velocity was a step down from his 97+ mph heat in 2009-2011, pitchers often have to slowly build their arm strength up again to pre-surgery levels and there was no reason to believe he wasn’t on track to doing so. When his velocity failed to reach that level through most of his 2014 campaign, though, it became unclear if he would ever regain his pre-surgery stuff.

By some measures, his time in AAA was a success. He struck out 9.73 batters and walked only 2.51 per 9 innings. He produced a 3.14 ERA compared to the Pacific Coast League’s league-wide 4.64 ERA. His biggest problem was home runs—he gave up 6 in only 28.2 innings. When was he called back up to the major league squad on July 4, there were reasons to be cautiously optimistic that he could find some success again as a reliever. The Rangers noted that he was throwing in the mid 90’s some games while in others he would sit in the low 90’s.

Feliz didn’t exactly dominate during his early outings. Through July 23, he had pitched 10.1 innings with only 4 strikeouts, 3 walks, and 2 home runs given up. Yet, out of the playoff race, Texas dealt their closer Joakim Soria to the Tigers and anointed Feliz their new closer. While it’s possible that the team merely liked his shiny ERA at the time over his FIP (2.61 to 5.75), perhaps they started to see some signs of life in him. Regardless, his 1.69 ERA and 13 saves out of 14 save opportunities the rest of the way probably made them feel validated in their decision. With his end of the season performance, it appears likely that he will be the Rangers’ opening day closer.

Projecting into 2015, Feliz’s 4.90 FIP and -.1 WAR from 2014 provide red flags. His home run rate also look to be an issue. His extreme flyball tendencies (51.1 FB% versus 27.3 GB%) resulted in 1.42 HR per 9 innings despite a fairly ordinary 11.1 HR/FB% rate. His 17.2 K% and 9 BB% doesn’t exactly inspire confidence, either. Steamer isn’t a fan and projects him for .1 WAR in 65 innings.

But there are reasons for optimism, too. He kept up his low BABIP streak at .176 (.215 career) thanks to his impressive 20 IFFB% (17.8 career). Among relievers with 200 innings since his debut, he has the lowest BABIP, the 6th lowest LD%, and the highest IFFB%. Steamer projects him for a .284 BABIP next year, but I’m willing to bet his will be much lower than that figure and will continue to let him beat his FIP by around a full run.

Next, we’ll look at his home run rate. His 2014 figure was the highest of his career, caused primarily by his 11.1 HR/FB% (6.9 career). What may have caused that? Well, it may have been caused at least in part by his changeup. A changeup is a pitch designed to fool hitters who are looking for a fastball: it is supposed to be thrown with identical arm speed as the fastball to make it harder to pick up, and then its velocity and/or movement difference makes it effective. For a pitcher throwing in the upper 90’s with hitters already struggling to catch up to their fastball, a changeup may be less effective because the velocity reduction may sometimes help the hitter instead of hurting him (of course, there are exceptions). When Feliz was throwing in the upper 90’s in 2009-2011, he threw his changeup just 4.4 percent of the time. When Feliz was throwing in the low to mid 90’s in 2014, he threw his changeup 12.4 percent of the time. For his career, opponents have a .212 ISO against his changeup compared to a .119 ISO against his fastball. In 2014, hitters had a .429 ISO against the pitch, including 3 of his 5 home runs given up on the year.

His velocity provided another reason for optimism as well. While his early- to mid-season velocity wasn’t great, he improved as time went on: in July he averaged 92.88 mph; in August he averaged 93.7; and in September he averaged 95.81. The ISO against his fastball decreased each month as well (from .107 to .107 to .053), even as he increased his usage of his fastball (from 64.7% to 77.36 to 77.78). His velocity increase had an added bonus as well: it allowed him to use his changeup less (from 14.72% to 11.32 to 3.17). The biggest question is whether he can maintain his September velocity, or even improve upon it.

Overall, I don’t think Neftali Feliz is a safe bet to be great in 2015. But I do think that he has a real chance to be much better than the projections project him to be. To end this post, I’ll post a few gifs of Feliz at his best in 2014:

* All pitch usage, velocity, and movement numbers are obtained from Brooks Baseball. All pitch results numbers are obtained from Baseball Savant.