Taking Stock of the Next Crop of Diamondbacks Starting Pitchers

Evaluating and taking a look at the Arizona Diamondbacks next crop of prospect starting pitchers.

Amarillo Sod Poodles Yilber Diaz (17) pitches the ball in a Texas League Championship game against the Arkansas Travelers, Tuesday night, September 26, 2023, at Hodgetown, in Amarillo, Texas. The Arkansas Travelers won 6-5. / Carter Pirtle for the Amarillo

Jack Sommers recently wrote an article that evaluated the performance of the most recent crop of starting pitchers that the Arizona Diamondbacks had called up since late 2022. These five pitchers have made their debuts and worked to varying levels of success while being the first group to reach the big leagues relatively together.

So far, only Brandon Pfaadt has achieved mostly success, but even he struggled to start his career. Now, this article will take a look at the next wave of starting pitchers who are currently prospects in the D-backs organization.

These four pitchers serve as the next guard who will all debut within the next year or so. They will be GM Mike Hazen's second go-round of starting pitching prospects to reach the Majors as in-house developed pieces compared to acquiring a young starter as he did with Zac Gallen.

These four pitchers will be critical to the D-backs future success, especially if the team is unable to keep any of Zac Gallen, Merrill Kelly, or Jordan Montgomery past 2025.

Blake Walston, LHP, Age 22

Blake Walston was taken in the same 2019 draft as Slade Cecconi, however, Walston was a High School arm and thus is still just 22 years old. That gives him plenty of potential to still improve as he matures and gets older. Walston is a soft-throwing left-hander that has great breaking pitches.

The 22-year-old has pitched 31.2 innings over seven games in Triple-A with the Reno Aces. He had a cup of coffee with the D-backs over a one day sample this year in which he pitched 3.2 innings against the Dodgers in relief of Jordan Montgomery. He allowed two runs, four walks, three hits, and struck out five. The outing was more impressive than the final line, as written about here.

While in Reno over those seven games, Walston has done quite well according to the base metrics and taking into account the extreme batter-friendly confines that he plays in in the Pacific Coast League. He's 3-0 with a 3.69 ERA with 31 hits, three homers, 19 walks, and 31 strikeouts.

He's been dynamite at Reno, allowing hitters to hit just .197/.352/.324 against him. Since being sent back to Triple-A, Walston has pitched 11 innings and allowed just two runs on eight hits with four walks against 12 strikeouts. That's good for a 1.64 ERA.

Walston's curveball this season has been unhittable in the minor leagues. He's thrown 91 of them and not a single one has been turned into a hit. Plus, batters are whiffing on them 55.2% of the time. His slider has been nearly as good. Opponents have hit just .190 against it with a slug of .286 over his 78 pitches. They are whiffing on the slider 34.8% of the time. Both of these pitches are elite.

His changeup is roughly average, or slightly above average. While it's been hit for a higher clip at .263 average and slugged for .316, opponents are still whiffing at an above-average rate of 24.4%.

The issue for Walston lies with his below-average fastball. He's thrown the fastball over 55% of the time and it has been walloped. Hitters are batting .333 with a slug of .556 off of it. They are whiffing 24.2% of the time.

The issue is likely location mixed with an average velocity of just 89.5 mph. Walston will have to locate his fastball better to avoid being hit hard with such slow speed. If he can locate better, Walston has the makeup to be a solid back-end rotation starting pitcher for Arizona.

Cristian Mena, RHP, Age 21

The D-backs No.11 prospect per MLB Pipeline, Mena was acquired last winter in the Dominic Fletcher trade with the Chicago White Sox. The D-backs knew if they waited to acquire him, they wouldn't be able to and so far, it seems they were right.

Mena has been electric with his off-speed pitches this season, even in hitter heaven Reno and Triple-A. Mena has been dominant with a 3.80 ERA in the PCL over nine starts and 45 innings. He's allowed 39 hits, eight homers, and has struck out 45. He's 2-0. Over his last three starts, he's been even better with a 3.38 ERA over 16 innings with seven walks and 12 strikeouts.

Mena has been great with runners on base, allowing a batting average of just .208. He's been even better against right-handed batters who are slashing just .183/.276/.290 against him.

His weak spot has been against lefties as his fastball and changeup have struggled compared to his breaking pitches. Lefties are hitting .301/.414/.616 against him. But, Mena has the profile of a starting pitcher that can excel in MLB.

Mena's fastball averages just 92.7 mph which lends itself to being hit harder due to it's speed. He's thrown this pitch 23+% of the time and has been hit hard with a batting average of .429 and a slug of .857. Batters whiff just 15.9% of the time. The goal for him will be to further develop his fastball into an average or better pitch.

His changeup is roughly an average offering, garnering 17.2% whiff while limiting hitters to just a batting average of .250 and a slug of .313. It averages 90 mph which makes it a hard change without a lot of separate in velocity compared to his fastball.

Meanwhile, his breaking pitches, namely his curveball and slider, are vastly above average. Hitters are hitting just .116 off them while slugging only .186 with a 33.3% whiff rate. Those two pitches are already ready for MLB hitters if he can develop his fastball.

Yilber Diaz, RHP, Age 23

Diaz just won Texas Pitcher of the Week a couple of weeks ago, and he arguably should've won more with how good his season has been. The 23-year-old pitcher is in the midst of a breakout season, utilizing his elite breaking pitches with an upper-90s fastball that can touch 100 mph.

Diaz has been a strikeout machine in Double-A with the Amarillo Sod Poodles. Over 41.1 innings and eight starts, Diaz has racked up 62 punchouts against just 17 walks. He's given up just 31 hits and 17 runs with five homers in an extreme hitter friendly park.

Six times has Diaz struck out eight or more batters in a game. The advanced stats say that he has been unlucky to have an ERA of 3.70. His FIP is just 3.41 while his xFIP is an even better 2.96. Diaz has increased his strikeout rate by 11.9% to 36.9% while lowering his walk rate by four percent to just 10.1%.

Diaz has frontline starter potential if he can carry this momentum and ability to Triple-A and beyond. It will be tough for him to do, but he has the highest upside at starting pitcher in all of the D-backs organization not named Zac Gallen or Brandon Pfaadt. MLB Pipeline's No.16 ranking for him will not be that low for much longer.

Yu-Min Lin, LHP, Age 20

Lin is the D-backs No.4 prospect according to MLB Pipeline. The slender and diminutive left-hander has been a star prospect for the D-backs the last couple of seasons. Lin had lofty goals this Spring Training to debut in the Big Leagues this year. Unfortunately for him, it might not come to pass.

Though, it's not because of anything he did, but rather a freakish injury that resulted from a foul line drive that nailed him in the face while he was in the dugout. According to Steve Gilbert, Lin ended up suffering jaw and sinus fractures that required surgery and would keep him out for six weeks or so.

When Lin has been healthy, he hasn't been as good as he was last year. Over his four starts and 18 innings, he had a 7.00 ERA with 27 hits, 14 runs, and five walks given up against 21 strikeouts. Still, his FIP portends great things as it sits at 3.88 and his xFIP sits at 3.15. Lin has the makeup to be a mid-rotation start or No.4/5 for the D-backs for a long time.