Arizona’s been on the fence about the direction they plan to go at the deadline, however, MLBTradeRumors and Ken Rosenthal report they plan to sell. The D-Backs fell to the Astros last night, getting swept in the series and falling to 5.5 games out of the wild card. With a multitude of pitchers on the injured list, they’ve decided to look to the future and capitalize on the impending free agents they have like Eugenio Suárez, Merrill Kelly and perhaps Zac Gallen, who could return a healthy dose of prospects to help out in the long run.
We began the “On the Block” series with third baseman Arizona Diamondback Eugenio Suárez and now we continue with another, starting pitcher Merrill Kelly.
Merrill Kelly, SP, ARI (Age 36, FA after 2025) – 21 GS, 122.0 IP, 9-5 W-L, 3.32 ERA, 3.48 FIP, 1.06 WHIP, 8.70 K/9, 2.73 BB/9, 0.96 HR/9
At age 36, Merrill Kelly perhaps does not have much of a future to look forward to in the majors, but if he keeps pitching the way he has this season, there’s a chance he does.
In 21 starts and 122.0 IP, the right-hander has put up an impressive 3.32 ERA, 3.48 FIP and 1.06 WHIP. His strikeout rate (24.2% K%) is a couple ticks above his average and he’s done a good job limiting home runs to about one every nine innings (0.96 HR/9). Kelly’s been very consistent with his walk rate throughout his career and he sits right at his career average (7.6% BB%).
He has consistently posted a ground-ball rate around 43–44% across his career, and only allows balls to be hit hard about 35% of the time. If there’s one potential red flag, it’s his .248 BABIP, which hints at mild regression but nothing extreme.
One important note is that Kelly has valuable postseason experience. When the Diamondbacks made the World Series in 2023, Kelly made 4 starts, pitching 24 innings to a 2.25 ERA, striking out 30.8% of hitters, and allowing a WHIP of 0.83.
Key Splits
Kelly’s been better against righties, although he’s still done well against lefties.
Against righties, he boasts a 2.70 FIP, striking out 27.5% of hitters, walking just 7% and allowing a .249 wOBA.
Lefties don’t strike out at the same rate against him (21.3% K%), but he still pitches to a 4.19 FIP (3.94 xFIP) and allowing a .297 wOBA.
He hasn’t been great with runners in scoring position this season (22.0 IP), pitching to a 5.73 FIP (4.20 xFIP), allowing a .267 BA, .523 SLG and .362 wOBA. It’s something to note, especially considering there may be high-leverage spots he’s put into.
Pitch Profile
Similar to the other pitchers I’ve already highlighted in this series (read about Keller and Houser), Merrill Kelly doesn’t boast a super-heater fastball or overwhelming stuff. He uses a 6-pitch mix–his 4-seam fastball has always been his most used pitch, but as he’s gotten older, he’s learned to play his changeup, cutter, curveball and slider (which he began throwing a couple years ago) off of that primary 4-seam.
Dissimilar to the other pitchers I’ve already highlighted in this series is that Kelly actually earns his value not from his fastball, but from his breaking and offspeed stuff. Kelly’s in the 98th percentile in offspeed run value and 83rd in breaking run value, according to Baseball Savant:
Kelly’s changeup is surrendering just a .335 xSLG (expected SLG), and .281 xwOBA (expected wOBA), making batters miss 34.0% of the time. He’ll throw that changeup to lefties primarily, having the baseball peel away from them before they can identify it. Take a look at where his changeup finishes compared to his fastball:
Those two pitches are identical until the hitter sees the ball go into the catcher’s mitt. For a similar effect, Kelly will throw his slider to righties, so they’re swinging at air before they realize it. That’s a deadly combo and can be incredibly effective come October.
Role Projection
Merrill Kelly has been fantastic as a starting pitcher for the Diamondbacks this season, but on a postseason roster with 3–maybe 4–starters, he projects to fill in as an emergency starter or bulk-inning reliever in October.
FanGraphs has his 1st Time Through Order ERA at 3.30 (.264 wOBA), his 2nd Time Through Order ERA at 2.55 (.244 wOBA) and his 3rd Time Through Order ERA at 4.78 (.345 wOBA). His strikeout rate drops significantly as he goes through the order (27.5% 1st Time Through down to 18.3% 3rd Time Through).
What this data tells us is that he’s much more effective earlier in games–as any starting pitcher would be–but he shouldn’t be trusted to go out and pitch deep into a playoff game where every inning could make or break your season. Ideally, a postseason roster has a healthy, reliable bullpen that can be turned to after Kelly does what he needs to do.
Outlook at the Deadline
Kelly is one of the more attractive arms on the market at the deadline. There isn’t a ton of reliable starting pitching that would be as cheap as this guy, considering he’s a rental. Look for a contending team in need of an innings-eater to take strain off of their other starters and their bullpen like New York Mets, the New York Yankees or the Boston Red Sox.
Inner Half 