Jhonathan Diaz: Red Sox Prospects

Most 22-year olds in Single-A don’t have bright MLB futures. However, left-handed pitcher Jhonathan Diaz is the exception to that rule. Despite his advanced age, the former international free agent should see his stock rise over the course of the 2019 season.

Red Sox Prospects Master List

Red Sox Prospects: Jhonathan Diaz

Diaz took a while to climb through the Red Sox system, but that’s not entirely his fault. The Venezuela native made his Red Sox debut in 2014 and put up some fantastic numbers. Starting 14 games in rookie ball, Diaz finished the season with a 1.63 ERA and a 2.83 FIP. He had a solid 7.33 K/9 and a 2.17 BB/9. By all accounts, Diaz showed he was ready to start 2015 with the Low-A Greenville Drive. 

However, Diaz never got that opportunity. The lefty suffered a serious knee injury during a fielding drill, costing him the duration of the 2015 season. Because of this injury, Diaz spent all of 2016 in rookie ball, slowly working on finding his form again. 

Diaz spent all of 2017 with the Greenville Drive, but he wasn’t quite the same. He finished the year with a 4.57 ERA and a 3.52 FIP, and the team opted to keep him in Greenville for 2018. Diaz finally bounced back, posting a 3.00 ERA and 3.14 FIP through 153 innings pitched. His K/9 was the highest of his career (8.65) while his BB/9 stayed at an acceptable 2.29. He earned a late-season promotion to the High-A Salem Red Sox, but only made one start. 

Still, 2018 showed that Diaz appears to be back on the right track. Most 22-year olds in Single-A don’t have bright MLB futures, but Diaz is the exception. That knee injury literally cost him years of development. If he can continue to stay healthy, he should start climbing through the minor league ranks as a solid clip.

Diaz is a four-pitch pitcher, but none of his pitches are particularly exciting. His fastball sits in the low 90’s, but has room for improvement. He complements his fastball with an average changeup, curveball, and slider. Diaz is willing to throw these pitches in just about any count and has decent control with all of them. None of these pitches are true put-away pitches, but they’re all serviceable in a four-pitch mix. 

What To Work On

Diaz should enter 2019 trying to prove that he’s officially put his knee injury in the past. 2018 was a big step in the right direction, but he’s still yet to face talent above the High-A level. 

Diaz’ pitch tool gives him a somewhat limited ceiling. As previously mentioned, he has four decent pitches, but nothing that blows you away. Because of this, he isn’t a natural fit for a bullpen role. Most starters-turned-relievers end up making the transition because they have one amazing pitch but nothing to complement it. 

Diaz doesn’t have that one amazing pitch that could turn him into a sure-fire major league reliever. If he’s going to make it, he’ll need to improve his control. As it is, he has average control, which just might not be enough for his pitch tool.

Diaz’ Projection

While Diaz doesn’t have the highest ceiling, he has significantly more potential than the average 22-year old Single-A prospect. The lefty’s development was significantly slowed by a devastating knee injury, but he should be back on the right track. 

If and when he makes the majors, don’t expect him to make that big an impact. His underwhelming pitch tool limits his ceiling, but he can still make a major league impact. His fastball has room to grow, and his pitches play well off each other. 

He’ll never be a top of the rotation guy, and his fastball will probably never be good enough for him to be an elite reliever. Whenever Diaz makes the majors (probably 2021), look for him to serve as starting pitching depth or a long arm in the rotation. Basically, he’s Brian Johnson.

Red Sox Prospects Master List

Featured image courtesy of Minor League Baseball

Dave Latham

Engineer by day, sportswriter by night. Follow me @DLPatsThoughts

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1 Response

  1. December 11, 2018

    […] Jhonathan Diaz Prospect Report (Rank: 21) […]

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