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Oakland A’s prospect watch: Sleeper relievers to follow throughout the farm

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One arm to watch from each A’s minor league affiliate.

Kyle Finnegan has been promoted to Triple-A.
Photo by Christian Petersen/Getty Images

The Oakland A’s bullpen was historically great in 2018, but it hasn’t yet been able to repeat that act so far this season. The A’s lead the AL in blown saves, and even the top arms have struggled. That all serves as a good reminder that relievers can be volatile performers, both for better and for worse, and that it’s best to have a lot of depth and backup plans.

With that in mind, let’s take a look at what the farm has to offer. There aren’t a lot of obvious, big names in this department, like the up-and-coming Lou Trivino last year. Only one pure reliever made our preseason Community Prospect List, and that was Miguel Romero in the very last spot on the Top 30.

The best bet for impact help in 2019 might come from some of the big-name starters rehabbing long-term injuries. In particular, A.J. Puk will begin rehab on Tuesday in High-A, and he’s expected to pitch as a reliever this year to limit his innings in his return from Tommy John surgery. Daulton Jefferies is also dominating in three-inning stints in Double-A, in his own return from TJS.

However, let’s look a bit deeper, at some sleeper options throughout the system. Not all of these guys are viable hopes for this summer, but they’re all worth keeping an eye on, and any pitcher in the upper minors could theoretically be a hot streak away from getting a look in the bigs. Here’s one key name at each level of the A’s farm.

Triple-A Las Vegas: Kyle Finnegan

The right-hander has been in the A’s system for a while now, since being drafted back in 2013. He switched to relief full-time in 2016, and he’s been consistently good in Double-A each year since. However, he hasn’t yet managed to make the successful jump to Triple-A, as all of his attempts at that level have resulted in him washing out back down to Midland.

Finnegan, 2016-18 AA: 2.52 ERA, 103⅔ ip, 105 Ks, 39 BB, 7 HR
Finnegan, 2017-19 AAA: 5.88 ERA, 41⅓ ip, 38 Ks, 24 BB, 6 HR

Now age 27, he stepped it up even further in Double-A this season.

Finnegan 2019 AA: 1.86 ERA, 19⅓ ip, 31 Ks, 6 BB, 0 HR, 8-of-10 saves

That performance earned him yet another call to Triple-A last week, and with it his next chance to prove himself at the highest level of the minors. His first appearance was shaky — he let four of his seven batters reach base, including two walks, but got through it without allowing a run thanks partly to two of those runners getting caught stealing. But that’s just one game, and he’s clearly someone to keep an eye on in Las Vegas.

The main detail attached to Finnegan’s name the last few seasons has been his velocity, which has reached triple-digits in the past. What’s new this year is that he’s added some movement to his fastball, while still sitting around 97 mph. Whether that extra wrinkle on his heater explains the spike in strikeouts remains to be seen, but it certainly offers a reason to hope that his third tour of Triple-A will go better than the previous two. And if it does, then he’s only one step away from helping out the beleaguered bullpen in Oakland.

Honorable mention: Miguel Romero. He’s left out here because he made the actual CPL last winter and thus isn’t quite a full-on sleeper in the sense I’m looking for in this post, but the 25-year-old righty is racking up strikeouts in Triple-A (42, in 30⅔ innings). Unfortunately, he’s also racking up walks (19) and homers (6), adding up to questionable results (4.11 ERA, 5.61 FIP). His assignment to Vegas was an aggressive one, though, so he deserves plenty of patience while he learns to harness his powerful stuff against top competition in an extremely hitter-friendly environment.

Double-A Midland: Zack Erwin

The A’s acquired him after the 2015 season, in the Brett Lawrie salvage trade, and he’s basically the polar opposite of Finnegan in terms of style. Erwin is a lefty who was billed as a soft-tossing starter, relying on plus command and deception rather than pure heat. Unfortunately, rather than hopping on the fast-track to an MLB rotation, he got consistently roughed up in High-A and also dealt with some injuries along the way. His High-A resume was ugly, in 43 games (41 starts) between ‘16 and ‘18.

Erwin, 2016-18 A+: 5.84 ERA, 215⅔ ip, 166 Ks, 68 BB, 26 HR, 4.90 FIP

Now age 25, it was time to move on from starting and try something new. He switched to the bullpen, and Erwin the Reliever has been a completely different pitcher.

Erwin, 2019 AA: 3.00 ERA, 27 ip, 40 Ks, 8 BB, 3 HR, 3.01 FIP

It’s not just the improved ERA, it’s how he’s getting there. His strikeout rate has nearly doubled from last year, from 7.2 K/9 (17.9% of batters) up to 13.3 K/9 (33.6% of batters), all while keeping his walks customarily low. His swinging-strike rate isn’t quite as elite (11.3%, good not great), but it’s still a couple points higher than he ever showed in Stockton. And he did all of this in the upper minors, at a higher level of the system than he’d ever pitched before, against the toughest competition he’s ever faced.

Normally when a starter converts into a high-strikeout reliever, you’d expect the explanation to be a spike in velocity in the shorter outings. However, that’s not quite the story here, as Midland catcher Collin Theroux attributes at least some of the success to other factors:

“Lowering his arm slot has worked wonders for him,” said Theroux. “I think he’s more deceptive this year. He’s always been a solid strike thrower so adding some deception into his delivery has lead to more swings and misses and weak contact. He’s developed a shorter cutter to compliment his bigger slurve that has been really effective getting in on righties and setting up his other stuff.

“I think with his long limbs (6’5 height) it’s been harder to pick up his new arm slot. I know in spring training I faced him when he first started lowering his slot and I had trouble picking his stuff up.”

The A’s are extremely thin on left-handed relievers, with basically nobody behind the current MLB duo of Ryan Buchter and Wei-Chung Wang, so it will be interesting to see how long they wait before giving Erwin a look in Triple-A.

Honorable mention: Jesus Zambrano. He’s been kicking around the lower levels of the system for a while now, but the 22-year-old might finally be putting things together. He had a solid showing in Single-A Beloit last summer, and then impressed in Stockton to begin this year (1.88 ERA, 28⅔ ip, 31 Ks, 8 BB, 2 HR). That earned him a ticket up to Midland, where he’s held his own through four games (6⅔ ip, 1 ER, 4 Ks, 2 BB).

High-A Stockton: Wandisson Charles

Like Finnegan, he’s known for his velocity. The 6’6 right-hander has been clocked as high as 102 mph, with the question being whether he can learn to control it for strikes. Here’s a profile from pre-2018, by Melissa Lockard of Oakland Clubhouse, which includes mentions of Dodgers All-Star closer Kenley Jansen. Here’s some video from last summer.

Indeed, Charles has put up enormous walk rates alongside his massive strikeout rates. Last year in Single-A Beloit, he walked 17 in 11 innings, nearly one-third of the batters he faced, while striking out 19. This year in Beloit his ratios improved, though they didn’t leave the danger zone with nearly a walk per inning: 22⅓ ip, 37 Ks, 20 BB. Even still, he got the call up to Stockton, and the early returns are promising:

Charles, 2019 A+: 1.23 ERA, 7⅓ ip, 12 Ks, 4 BB, 0 HR, 2 hits

At the very least, nobody really makes any contact against him. But the 22-year-old is one step closer to adding an “effectively” in front of his “wild,” and if he ever gets there then look out.

Honorable mention: Will Gilbert. Mostly including him here because he’s a lefty, but the 25-year-old (2016, 8th round) is putting up decent numbers for Stockton (19 ip, 23 Ks, 9 BB, 2 HR, 3.82 FIP).

Single-A Beloit: Eric Marinez

This is the most interesting story on an already colorful list. He began his career as an infielder whose best tool was a strong throwing arm, but he wasn’t getting anywhere as a hitter. In 2018 he was slapped with an 80-game PED suspension, and when he returned to action he dabbled in the outfield. Finally, toward the end of last season, the Ports tried putting him on the mound, where he “sat 92-95 mph with a decent slider,” reports broadcaster Zack Bayrouty. Here’s some video from last October via pro scout John Eshleman, including a 96 mph heater, a sinker, a change, and a curve.

Now Marinez is a full-time pitcher, and the early results are promising. He’s serving as Beloit’s closer, and his performance earned him a nod for the Midwest League All-Star Game.

Marinez, 2019 A: 2.73 ERA, 27 ip, 38 Ks, 18 BB, 0 HR, 9-of-10 saves

There are still some walks to clean up, but that’s a wonderful debut line for a 23-year-old in his first foray into professional pitching. Can he be the next Sean Doolittle-esque position player convert, rising up the system quickly once he gets the hang of things?

Honorable mention: Michael Danielak. The right-hander was a 19th-round draft pick in 2017, and he put up huge numbers in Low-A Vermont that summer. He was then slowed by injuries last year, but now he’s back and better than ever in Beloit. He gave up a run this morning to finally push his ERA over 1.00, but his line is still eye-popping (1.25 ERA, 21⅔ ip, 32 Ks, 5 BB, 2 HR, and FIP was 2.29 entering the day). You could argue that he should have led this section and Marinez should have been honorable mention, but I went with Marinez because of the closer status, the All-Star bid, and the fact that I just had way more to say about him. As always with players in Single-A, for both of them the next impressive thing they can do is get promoted to Stockton.

This also seems like the time to mention that Beloit has a reliever named Jaimito Lebron, which is basically LeBron James but in Spanish and in reverse. The 22-year-old right-hander has good numbers, too: 2.11 ERA, 21⅓ ip, 29 Ks, 8 BB, 0 HR, 2.02 FIP.