With one-third of the 2025 MLB season now complete, we're seeing more transparency in which teams are trending towards selling or buying at the July 31 MLB trade deadline. At the start of the year, the Arizona Diamondbacks, who shocked the baseball world with a monster deal to land Corbin Burnes, were considered a strong competitor in the NL West. Unfortunately, that has not been the case, as the D-backs find themselves with a 28-31 record, currently eight games back in the division, and five games back in the Wild Card.
The outlook on the season could grow increasingly grim if the D-backs don't receive good news on Burnes' elbow injury. As rumors begin circulating, it doesn't take much more than common knowledge to know that if the Diamondbacks are sellers, their long list of pending free agents may cause a fire sale at the deadline. Starting pitching is always a priority for teams, so let's begin by discussing Arizona's starting rotation, which has two names that will be sought after.
1. Merrill Kelly
Merrill Kelly has been a mainstay in the Diamondbacks' starting rotation for his seven-year career. If he isn't extended, Arizona will need to make the tough decision not to lose him without obtaining a decent prospect in return. Kelly will be eligible for a qualifying offer, but given he is in the midst of another above-average season, it wouldn't be wise for him to accept if he is looking to cash in on the open market.
Kelly owns a 3.49 ERA dating back to 2022, and currently sits at 3.78 in 2025. His FIP, however, is lower at 3.56, suggesting a bit of bad luck has occurred along the way. Kelly, when healthy, is a workhorse that can get up to and surpass 170 innings in any given season. He is the perfect middle of the rotation arm that teams can likely obtain without breaking the bank, and he will only be owed a little over $2 million for the remainder of the season by the team that acquires him.
2. Zac Gallen
Currently being paid just $13.5 million by the Diamondbacks, long-time staff ace Zac Gallen is experiencing a down year. He will likely receive interest at the deadline if available, but he will not be every team's first option unless he turns things around between now and then. Although Gallen's FIP (4.58) is lower than his ERA (5.54), he is still well off from his career 3.29 ERA he had going in 2025.
Key changes from Gallens 2024 to 2025 include:
2024 BB%: 8.7
2025 BB%: 11.0
2024 K%: 25.1
2025 K%: 22.6
2024 ground ball%: 46.2
2025 ground ball%: 40.2
2024 Hard-hit%: 41%
2025 Hard-hit%: 45.3
2024 Pitching run value: 8
2025 Pitching run value: -7
The big red flag here is the walk rate, which began to plummet in 2024 but has risen to an awful level in 2025. At Gallen's best, he was recording walk rates of 5.6-6.6 percent between 2022-23, and this is a significant catalyst for the lack of production this season. Blaming bad luck and FIP is only part of it. Gallen must get back to doing what he does best, minimizing base runners. In 2022, Gallen's 0.913 WHIP led the National League, and his 1.395 WHIP in 2025 isn't even on the same planet.
Gallen has a good feel for his slider, allowing just a .191 batting average, as opposed to the .310 from last season, but is only throwing the pitch 9.9 percent of the time. Mixing in a few more sliders may be a way to reset and get hitters off balance. His five-pitch mix is ideal for any starter, but utilizing his four-seamer nearly 50% of the time doesn't offer much challenge for hitters who will wait for that pitch, knowing it's coming at some point.
Therefore, it's no surprise the fastball has been Gallen's worst pitch by Pitching Run Value with a mark of -5. If Gallen can lower the fastball usage and mix in higher percentages of his secondary pitches, it can lead to success. If he finds that success, the Diamondbacks will have one of the most coveted arms available at the deadline.
3. Josh Naylor
In terms of bats, Josh Naylor and his $10.9 million to avoid his final year of arbitration in 2025 appears to be at the top of the list. He slashes .297/.355/.464 with seven home runs, 37 RBIs, and nine stolen bases. For teams needing a lefty 1B/DH, Naylor provides decent pop while hitting for a high average. Left-handed bats are typically their own commodity, so don't be surprised to see his name floated at the deadline if the Diamondbacks sell.
4. Shelby Miller
Regarding relief arms, Shelby Miller is the guy to have circled on your radar. Currently having a fantastic season in his age-34 season, Miller owns a microscopic 1.90 ERA in 23 innings of work. That mark is down 2.15 runs for his career, 4.05 ERA, so something has improved. Shelby is only earning $1 million for 2025, which means he'll be owed next to nothing by the time he is moved.
Fantastic relievers owed less than $500,000 for the rest of the year are hard to come by, and Miller is just another strong piece in Arizona for a team that has underperformed. There is still time for the Diamondbacks to turn things around, but they are teetering towards selling. If they pull the plug at the deadline, they will be in a favorable position to retool for next season, given the prospect haul they could receive.