The Diamondbacks optioned Jameson to Triple-A Reno on Sunday, Alex Weiner of ArizonaSports.com reports.
After being limited to 17 total innings between three levels in 2025 while contending with elbow problems, Jameson has been healthy for spring training but didn't pitch well enough to win a spot in the Opening Day bullpen. He'll head to Reno after turning in an 8.44 ERA, 2.44 WHIP and 5:5 K:BB in 5.1 innings over five Cactus League appearances.