Blue Jays 2017 top prospects: #29, RHP Yennsy Diaz

Blue Jays pitching prospect Yennsy Diaz brings raw talent and upside to the lower levels of the prospect pool

The Toronto Blue Jays added pitcher Yennsy Diaz out of the Dominican Republic early in the 2014 signing period, and after his first two professional seasons, the right-hander remains a pure upside project.

It’s our intent to balance the latter third of this top-30 prospects list with ‘safe’ prospects (college picks, etc.) and players that remain raw projects. With a year and a half of development since the farm-thinning trades of 2015, the Blue Jays have plenty of both.

Diaz brings exactly what you would expect from a prospect at this level in the rankings: an equal dose of intrigue and question marks.

Name: Yennsy Diaz
Position: RHP         Age: 20
Height: 6’1”    Age: 160 lbs.
Throws: Right            Bats: Right
Acquired: 2014, International FA

In 2015, Diaz’s first pro season began in the Dominican Summer League, he got off on the right foot. Over 37.1 innings, he posted a 1.93 ERA with 39 strikeouts and earned a trip to the Gulf Coast League.

Diaz’s numbers were not as strong with the GCL Blue Jays, but his strikeout totals stayed afloat and, on the whole, his debut was a success.

Year Age AgeDif Tm Lg Lev Aff W L ERA G GS SV IP H R ER HR BB SO WHIP HR9 BB9 SO9
2015 18 -1.5 2 Teams 2 Lgs FRk-Rk TOR 4 4 2.88 15 9 1 56.1 54 25 18 0 23 58 1.367 0.0 3.7 9.3
2015 18 -1.0 Blue Jays DOSL FRk TOR 3 3 1.93 10 6 0 37.1 30 14 8 0 16 39 1.232 0.0 3.9 9.4
2015 18 -2.4 Blue Jays GULF Rk TOR 1 1 4.74 5 3 1 19.0 24 11 10 0 7 19 1.632 0.0 3.3 9.0
2016 19 -2.0 Bluefield APPY Rk TOR 4 6 5.79 12 10 0 56.0 59 39 36 9 27 48 1.536 1.4 4.3 7.7
All Levels (2 Seasons) 8 10 4.33 27 19 1 112.1 113 64 54 9 50 106 1.451 0.7 4.0 8.5


The fastball is Diaz’s go-to pitch. Not only is it his best pitch by a wide margin, but he leans on it very heavily unless he’s forced to do otherwise. When the pitch is ‘on’, that’s a fine strategy as it reaches 96-97 MPH (sits 91-94 MPH) with some slight tailing action that could develop further with time.

“He’s a young kid and sometimes he wants to overthrow,” Bluefield pitching coach Tony Cacares told Baseball America following an August start, “and when he overthrows he gets rotational and he gets on the side of the ball. We’ve been trying to get his mechanics top to bottom more so he can finish out front with good spin on the ball.”

When Diaz is missing up in the zone, Cacares notes, his fastball tends to flatten out and become an easier pitch to hit. Without well-developed secondary pitches, a flat fastball means a short night.

Diaz’s changeup and curveball will determine how far he goes as a starting pitcher. If both pitches can advance to even an average level, it’s conceivable that he pushes through to the upper-minors in a rotation role and rides that development path as long as he can.

That may not be the likeliest outcome long term, however, which doesn’t necessarily kill his prospect status. There is plenty of room in baseball for bullpen prospects, especially with the relief market being one of the most inflated areas of free agency.

In that vein, a solid fastball-curveball combination might just be the key for Diaz over the next couple of seasons. Beyond that, some physical growth will also go a long way.

Diaz is still listed at 160 pounds, a number that the Blue Jays would surely like to see reach 175 or above. Adding bulk won’t necessarily boost his velocity, but it could allow Diaz to maintain it with greater ease and focus more on movement.

By this time next off-season, Diaz could rank anywhere from the top-20 to well off the list, but his bullpen potential is worth monitoring closely.

BLUE JAYS TOP PROSPECT LIST:

#30: RHP Jordan Romano

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