Diamondbacks Eye Gallen, Kelly, and Giolito to Bolster Rotation

The Arizona Diamondbacks are actively evaluating ways to improve their starting rotation during the 2025-26 offseason, with free agency providing several intriguing options. With Zac Gallen declining his qualifying offer, speculation has emerged that the right-hander could return to Arizona, potentially alongside former starter Merrill Kelly.

MLB Insider Robert Murray highlighted the likelihood of such a reunion during a recent appearance on Foul Territory, suggesting both pitchers are realistic targets for the Diamondbacks while acknowledging the competitive nature of the free-agent market. The club’s interest in Lucas Giolito adds another layer to their potential offseason plans.

Arizona’s rotation currently lacks depth, making strategic acquisitions essential for sustained competitiveness. Bringing back proven arms familiar with the organization could offer immediate stability while complementing younger talent already on the roster.

As the offseason unfolds, the Diamondbacks’ front office faces critical decisions that could shape the team’s pitching landscape. Rumors surrounding Gallen, Kelly, and Giolito have put Arizona near the center of several high-profile free-agent conversations.

1. Zac Gallen’s Potential Return

Zac Gallen opted for free agency after declining his qualifying offer, leaving the Diamondbacks without a key piece of their rotation. The 30-year-old right-hander posted a career-high ERA of 4.83 in 2025, finishing the season with a 1.260 WHIP and 175 strikeouts over 192 innings. Despite a higher ERA, Gallen remains a reliable option in terms of innings and strikeout potential, making him an appealing candidate for teams seeking rotation stability. Murray noted that Arizona has not ruled out a reunion, signaling mutual interest between player and franchise. Gallen’s familiarity with the Diamondbacks’ coaching staff and defensive alignment could make his return smoother than integrating a completely new pitcher. This continuity might also provide confidence to the front office as they weigh options against other free-agent suitors. The right-hander’s contract demands are likely to be competitive, given interest from multiple teams, but a return to Arizona could offer him both familiarity and the opportunity to anchor a rotation in need of proven talent.

2. Merrill Kelly and Lucas Giolito in the Mix

Merrill Kelly, 37, also emerges as a potential target for Arizona, having completed the 2025 season with the Texas Rangers. Kelly finished with a 3.52 ERA, 1.114 WHIP, and 167 strikeouts over 184 innings pitched. The Diamondbacks traded him midseason in exchange for pitching prospects, but his familiarity with the organization could make a return mutually beneficial. Lucas Giolito is another free-agent arm reportedly on Arizona’s radar. Known for his strikeout ability and experience in high-leverage situations, Giolito could complement Gallen and Kelly to form a competitive rotation if the team successfully signs multiple targets. Murray emphasized that both Kelly and Gallen represent realistic re-signing opportunities, though the free-agent market will be active and competitive. Arizona will likely need to move decisively to secure any of these pitchers. The potential acquisition of all three arms—Gallen, Kelly, and Giolito—could transform the Diamondbacks’ rotation into a formidable unit capable of contending in the National League West while balancing experience and upside.

3. Implications for Arizona’s Rotation

The Diamondbacks enter the offseason with a rotation thin on proven depth, underscoring the importance of targeted acquisitions. Any moves involving Gallen, Kelly, or Giolito will define the team’s pitching identity for the coming season. Acquiring familiar pitchers like Gallen and Kelly offers immediate comfort and chemistry, while Giolito could provide a fresh dynamic to the staff. How Arizona balances these acquisitions with internal talent will be closely watched by fans and analysts alike. Offseason strategy, payroll considerations, and roster flexibility will all play into the front office’s decision-making process. The choices made in the coming months will signal whether the Diamondbacks intend to compete for a playoff spot immediately or gradually rebuild around younger pitchers. Arizona’s approach to free agency could set the tone for its rotation and overall competitiveness, making Gallen, Kelly, and Giolito pivotal figures in the team’s offseason narrative.