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May 28, 2015 at 8:30 AM

Scouting Scratch: High minors bullpen arms

In past years, the bullpen options in Portland and Pawtucket have tended to be more organizational players or solid depth options rather than true prospect types. This year, however, both teams have several intriguing bullpen options that could help the major league team at some point this year or next. This week’s scouting scratch will feature six of these pitchers based on looks from the first two months of the season.

Of all the bullpen arms I have seen, Pat Light is the most intriguing. A former supplemental first-round pick in 2012, Light really struggled as a starter even with plus velocity. He did not miss nearly enough bats and was very hittable, giving up a lot of hard contact due to his lack of command and movement with his fastball.

A move to the bullpen this year has revitalized his career, with Light showing off the stuff that led to him being a first-round pick. Light has always had fastball velocity, but has lacked refinement both with his arsenal and delivery. Out of the bullpen, those issues are minimized, as he does not have to worry about repeating his delivery deep into outings, and his lack of a third pitch is not an issue. Light’s fastball has always had plus velocity, generally working in the 93-94 mph range, with the ability to dial it up to 97-98 mph on occasion. When elevated, however, the pitch is still very flat, and he has been made to pay for it when he leaves it there, giving up three home runs this year in only 24 1/3 innings. Still, Light is missing many more bats in 2015 due to improved command and control, mechanical improvements, and drastic improvement with a secondary pitch, the re-introduction of his splitter.

Light threw the splitter in college, but shelved it when he entered pro ball to focus on developing his slider and his changeup. He did not make much progress with either offering, with neither showing consistency. His splitter, on the other hand, has been a revelation, showing true plus potential and the makings of a bat-missing out pitch at the big league level. He throws the pitch 84-87 mph with the same arm speed as his fastball before the bottom falls out of the pitch late.

With continued refinement, Light has the potential for at least two plus offerings and the upside of a late-inning reliever. He is already pushing for a call-up to Triple-A, but I would not expect to see him in the big leagues this year, mainly because he does not have to be added to the 40-man roster until this offseason.


Acquired from the San Francisco Giants in the Jake Peavy trade last year, Heath Hembree has quietly put together a very solid season with Pawtucket, though he has struggled during his brief stints in the big leagues. Hembree has a mature pitcher’s build with limited projection. He has short arm action with a slight hook behind and slightly above-average arm speed. He works solely from the stretch, from the first base side of the rubber. He has a live arm, generating easy velocity. His fastball sits 92-94 mph, topping out in the mid-90s with late life.

His slider is his best secondary pitch, possessing solid-average potential. He throws it in the mid-80s with short, horizontal break. With his fastball-slider combination, Hembree does not have late-inning upside, but he still could play a valuable role as a middle reliever as soon as this year.


He is currently on the DL, but Kyle Martin has been impressive pitching in multi-inning stints out of the Portland bullpen. The first thing that stands out with Martin is his physically mature frame—he looks all of the 6-foot-7, 235 pounds he is listed at. He has a controlled delivery from a three-quarters arm slot with slightly long arm action behind, but otherwise relatively clean mechanics.

His fastball generally works in the 92-94 mph range with late life, but has shown higher in some outings. He has good control of the pitch, but his command needs refinement. At its best, the pitch could sit mid-90s and grade out as a 65-70 fastball. His changeup also has plus potential, providing a great compliment to his fastball. He throws it in the low-80s with great separation. He has great feel for the pitch and the confidence to throw it in any count. It is very deceptive, thrown exactly the same as his fastball before it shows late drop and fade away from left-handed hitters.

His slider is a below-average offering, and I would not be surprised to see him scrap it at some point to focus on his fastball-changeup combination. With the new draft system, senior signs who sign for well under slot are very important, but Martin shows that these picks are not just throwaway picks, and even for a $10,000 bonus, with good talent evaluation and development, you can find a player who has big league potential.


One of the more unheralded prospects in the system, Jonathan Aro has quietly been fast-tracked, finding himself in Pawtucket in mid-May even though he started 2014 in Greenville. After signing out of the Dominican Republic, Aro has found success at every stop in pro ball, showing off a decent three-pitch mix that should play out of the bullpen. Aro does not have the look of a typical pitcher, listed at 6-feet, 172 pounds, although that weight seems very light. He has a sturdy build, with a thick lower half and minimal physical projection remaining. He works quickly with a short, jerky arm action from a high three-quarters arm slot. He has some natural deception in his delivery with the way he brings the ball behind his body.

Aro’s fastball works in the low-90s with arm-side run. The pitch jumps on hitters, and he is generally around the strike zone with it. He complements his fastball with a slider and changeup, with his slider the better of the two. His slider is a fringe-average pitch at present with solid-average potential. He throws it 83-85 mph with short, vertical break. His changeup shows drop at 83-84 mph, but lags behind his other two offerings and is more of a show-me offering. From seemingly out of nowhere, Aro now finds himself just one step away from the big leagues. This offseason the Red Sox have to make the decision whether to add him to the 40-man roster, and if he continues to pitch this well—he already has 10 strikeouts to a single walk and seven hits in 7 2/3 innings for Pawtucket—then he will either be added or will likely be selected in the Rule 5 draft.


Another member of the Pawtucket bullpen, right-hander Zeke Spruill has a shown two playable pitches. Spruill has a tall, lanky build with a skinny waist, but limited remaining projection. He has a simple delivery from a high three-quarters arm slot, with a short arm action behind and slight hook. His fastball works 92-93 mph primarily, topping out at 95 mph. The pitch has heavy sink, leading to a lot of weak contact on the ground (58.5% groundball rate), but does not miss many bats. His slider is a below-average offering that flashes average potential. He throws it 78-82 mph, but it has tended to be more of a slurvy, loose breaking ball both times I have seen him. Spruill is already on the 40-man roster, so it would not surprise me to see him up in the big leagues at some point this summer. He has shown the ability to go multiple innings in Pawtucket and could be a good innings-eating option if the big league bullpen is overworked.


In his second go-round in Pawtucket, Miguel Celestino still shows flashes of major league reliever upside, but he still has major consistency issues, which make the chances that he reaches his potential pretty low. Celestino has a rough delivery that he struggles to repeat. He has a long arm action and stab behind during which he shows the ball, making picking up his pitches relatively easy. He struggles to find a consistent release point and does not get great plane on his fastball despite his height. Even with those issues, Celestino does have arm strength, and you can’t teach that. Celestino can dial his fastball up to the high-90s, working primarily 93-95 mph. He has well below-average command of the pitch and only average control. Both of his secondary offerings—a slider and a splitter—flash average-to-better potential, but are also inconsistent. His slider comes in 84-87 mph with short 10-to-4 break, but he has a tendency to come around the ball and not snap it off. His splitter comes in in the high-80s and shows late drop, but he has the tendency to telegraph the pitch by slowing his arm. 

Photo credit: Pat Light, Kyle Martin and Zeke Spruill by Kelly O'Connor

Ian Cundall is Director of Scouting for SoxProspects.com. Follow him on Twitter @IanCundall.