Arizona Diamondbacks pitchers competing for the fifth rotation spot

The Arizona Diamondbacks have an outstanding 1-4 at the top of their starting rotation. Zac Gallen, Merrill Kelly, Eduardo Rodriguez, and Brandon Pfaadt head the rotation. But the fifth spot is a little more up in the air. Currently, there isn’t a definite number five starter for the Snakes. But there are a handful of players you could see as the team’s number five starter. A good Spring Training could change the tide of things, but as we approach the pre-season, here is who could secure the number five rotation spot for the Diamondbacks right now.

Tommy Henry

Tommy Henry might have the inside track for the 5th rotation spot. The left-hander didn’t do badly in his 2023 rookie campaign, and had he continued to pitch like that over a larger sample size, the role may have been his until he proved otherwise. But he was limited to just 89 innings last year, which leaves the opportunity for someone else to swoop in and overtake Henry.

Henry had a 4.15 ERA, 4.88 FIP, and 1.36 WHIP. He had a poor 16.8% K rate along with a below-average 9.2% walk rate. His HR/9, however, was slightly better than the league average, sitting at 1.21. Henry also had some solid batted ball numbers. He was in the 73rd percentile of exit velocity (87.9 MPH), 89th percentile of hard-hit rate (32.4%), as well as the 54th percentile of barrel rate (7.6%).

Although Henry had a solid ERA and was good at limiting hard contact, there are some underlying factors that are worrying. He had a 5.29 SIERA, 5.40 xFIP, and a a 130 DRA- (95 ERA-). Sure, while Henry would be filling the role of a 5th starter, and you’re not going to expect your 5th starter to be an ace, you’d probably want something a little better than an ERA above 5.00.

As of right now, I’d say that Henry is one of the more likely candidates to secure the 5th starter job. Given that he didn’t do poorly last season, he will give him a leg up on the rest of the competition. However, I definitely would not say he’s set in stone as the 5th starter. At the very most, it’s his position to lose.

Ryne Nelson

Ryne Nelson made the third most starts last season among any Diamondbacks pitcher, sitting behind just Gallen and Kelly. However, Nelson struggled in his first extended look in the bigs. Still, the right-hander is only 26 and was a top prospect not that long ago. He probably has the second-best chance of securing a rotation spot behind Henry.

Nelson pitched 144 innings last year, working to a 5.31 ERA, 5.07 FIP, and 1.42 WHIP. He had a strong 7.4% walk rate, however that’s about where the positives end. Nelson had a K% of 15.5%, the third lowest of any pitcher with 140+ IP last season. He also struggled to limit home runs with a poor 1.50 HR/9 rate. Batters hit Nelson hard, as he sat below the 10th percentile of both exit velocity (90.8 MPH) and barrel rate (11.6%), as well as just the 22nd percentile of hard-hit rate (42.7%).

Nelson’s bottom line was worse than Henry’s, but the underlying numbers paint a similar picture. Nelson had a 5.30 xFIP, 5.24 SIERA, and 125 DRA-,
all three of which were near carbon copies of Henry’s. Nelson also has better stuff in comparison to Henry. Stuff+ put Nelson at 102 while Henry was at 83.

Although Nelson struggled last year, I definitely think he has the potential to breakout in the future. He’s not too old and deserves a second shot. He will definitely be in consideration for the final rotation spot for the Diamondbacks heading into Spring Training.

Blake Walston

Blake Walston is another former first-rounder and another one of the D-Backs’ top prospects. He isn’t as highly regarded as Cecconi, but he still ranks top 30 among MLB Pipeline, FanGraphs, and Baseball America. Walston made it to Triple-A last year, where he posted some solid numbers and was added to the 40-man roster to protect him from the 40-man roster.

Walston pitched 149.1 innings in 30 starts, working to a 4.52 ERA, 5.39 ERA, and 1.58 WHIP. Keep in mind his ERA was over a run better than the league average in the PCL. But Walston had some worrying peripherals. He walked 14% of the batters he faced. On top of that, he had a K% of 15.6%. His 0.54 HR/9 looks great on paper, but he also had a 5.3% HR/FB ratio, so there’s bound to be some regression.

I would give him a little slack, though. This was the first time he ever pitched with the automated strike zone, and some pitchers had some trouble adjusting to that last season. Walston sits in the low 90s with his four-seam fastball, but his slider and change-up have the potential to be plus offerings. His curveball also has average potential.

Walston’s stuff took a step back from 2022, but he still has the potential to be a cog in the Diamondbacks’ rotation. Walston is still a little young as he won’t turn 23 until late-June. He has a longer shot to make the team’s starting rotation.