Diaz signed with the D-backs for only $10,000 as a 20-year-old Venezuela native in February 2021, and within three years, he’s carved out a prominent role for himself in the Arizona farm system. The right-hander eclipsed the century mark in innings last season, spending most of the campaign with High-A Hillsboro before getting a late cameo with Double-A Amarillo. His 31.8 percent strikeout rate ranked ninth among 272 Minor Leaguers with at least 100 frames, but his 4.82 ERA and 1.34 WHIP took some of the shine off.
Diaz has pushed from Double-A to Triple-A to even getting looks in the Majors, thanks to a continually refined arsenal. His fastball touches 99 mph, averages around 96 and comes with ample zip up in the zone. His 82-85 mph slider was much improved in 2023 and has become his most relied upon secondary offering in ’24 -- a two-plane breaker that batters just can’t handle. His upper-70s knuckle curve gives him another dropper that plays off the high heat and gives him an option against lefties. He rarely, if ever, uses a low-80s changeup these days.
The 6-foot right-hander’s control has been solidly improved at the upper levels this summer, and while there’s still effort in his delivery, he’s throwing enough strikes to remain in a starting role. The D-backs gave Diaz MLB looks before he became Rule 5-eligible this offseason, and while there’s still some refining needed, he should be a serious consideration for the rotation moving forward.
Diaz signed with the D-backs late for an international player as a 20-year-old out of Venezuela in February 2021, doing so for just $10,000. He went to the Dominican Summer League that season and walked more batters (18) than he struck out 17) in 26 1/3 innings as a reliever. Arizona still felt like there were the makings of a starter and got aggressive with the righty in his age-21 season, bumping him straight to Single-A Visalia, where that confidence was rewarded. Diaz struck out 99 batters and posted a 4.06 ERA over 77 2/3 innings between the California and Northwest Leagues.
Diaz has steadily gained velocity since joining pro ball and now averages 94-97 mph while flirting with triple digits. The heater bursts out of his hand and rides well to the top of the zone, making low-level hitters look foolish. He’s worked on adding a little extra velo to his curveball (it’s now in the upper 70s), as well as some sharpness, and that should end up being his best secondary the more he throws it. A more horizontal slider and average changeup give Diaz additional options.
Standing just 6 feet tall on the mound, Diaz can look like he’s overthrowing at times, and his command becomes scattershot as a result. The D-backs believe fatigue played a factor in his walk rate jumping at High-A, but it’s still not clear how the control will play against more patient upper-level hitters. Diaz’s velocity gives him a solid floor as a reliever.
How this works: Every pitch is affected by the forces of gravity,
which means that every pitch drops on its way from the mound to the plate.
These numbers are reported with gravity, which makes them larger and
different than other pitch movement numbers you may have seen. Since gravity
requires time, and slower pitches aren’t ‘better’ just because they have
more time to move, the movement of a pitch is compared to ‘average’ movement
by comparing it to other MLB pitch types within +/- 2 MPH and from within
+/- 0.5 feet of extension and release.
Note: xHR tells how many of this pitcher's home runs allowed would have been out of other stadiums. The "Adjusted" view here accounts for different wall heights, distances and environmental effects using Statcast Park Factor data.
Standard
Year
Team
Avg HR Trot
Actual HR
xHR
HR-xHR
Doubters
Mostly Gone
No Doubters
No Doubter %
2024
24.5
3
3.5
-1
1
4
1
33.3
Player
24.5
3
3.5
-1
1
4
1
33.3
Note: xHR tells how many of this pitcher's home runs allowed would have been out of other stadiums. The "Standard" view here accounts for different wall heights and distances but excludes environmental effects. It is based purely on the observed trajectory of the hit.
Note: xHR tells how many of this pitcher's home runs allowed would have been out of other stadiums. The "Adjusted" view here accounts for different wall heights, distances and environmental effects using Statcast Park Factor data.
Standard
Year
HR
2024
3
4
3
3
3
4
5
3
4
3
4
4
5
3
5
3
3
3
4
4
4
4
4
4
3
3
2
2
4
4
2
Player
3
4
3
3
3
4
5
3
4
3
4
4
5
3
5
3
3
3
4
4
4
4
4
4
3
3
2
2
4
4
2
Note: xHR tells how many of this pitcher's home runs allowed would have been out of other stadiums. The "Standard" view here accounts for different wall heights and distances but excludes environmental effects. It is based purely on the observed trajectory of the hit.
! Note: Shifts are through the 2022 season, Shaded starting from the 2023 season, Shift:
three or more infielders are on the same side of second base, Shade: positioned outside of
their typical responsible slices of the field. Learn more about
how positioning is defined here
AZ 
