The Seattle Mariners sold their affiliate and are part of a chain of shifts in the California League.
The Seattle Mariners and the Modesto Nuts announced today that the Mariners’ Low-A affiliate has been sold to Diamond Sports Group. The move comes with the more directly pertinent announcement that 2025 will be the final season for the Nuts in Modesto. The reigning California League champions will be moved to San Bernardino, CA, to functionally become the Inland Empire 66ers, though branding seems subject to some changing. The move is part of a series of changes across the California League, ongoing fallout from MLB’s consolidation of control over Minor League Baseball in recent years.
The Mariners’ Low-A affiliate will remain in the California League, which the club stated as a core priority, consolidating the M’s affiliates in the westernmost leagues possible at each level. Moving the Nuts to San Bernardino means that once again, Seattle will have an affiliate at Inland Empire, where the organization began initially after a move from another California town. The Salinas Spurs became the San Bernardino Spirit in 1987, and were the affiliates of the Mariners until 1994. After half a decade with the Los Angeles Dodgers, the then-Stampede returned to the Mariners from 2001-2006. During that time, their title changed from the San Bernardino Stampede to the Inland Empire 66ers of San Bernardino. That mouthful of a multilocational title presaged their more recent affiliation, as they’ve been the Single-A club for the Los Angeles Angels of Anaheim since 2011 after another few years back with the Dodgers.
The current Inland Empire club will be moving to Rancho Cucamonga, CA, echoing the founding of the Rancho Cucamonga Quakes in ‘87. The current Inland Empire organization will technically move to Rancho Cucamonga, remaining the Angels affiliate, while the Quakes will move to Ontario, CA and retain their Dodgers affiliation. The city of Ontario is in the midst of constructing a $100 million sports complex that will be centered around the new stadium for the Dodgers’ new affiliate.
This leaves Modesto the odd city out, a heartbreaking outcome for a city of over 200,000 residents which has seen continuous play since 1946, affiliated with MLB since 1948, and has been the home to six future Hall of Famers as players, as well as one of the first stops for Sparky Anderson in his pathway to the Hall as a manager. The Nuts have been the first stateside stop for many of the Mariners’ international players, as well as the first taste of pro ball for many draftees. It’s also the second time in the past half-decade that Seattle’s departure (as part of MLB’s broader shrinking of affiliated minor league baseball) has left their Single-A affiliate without a home, echoing the West Virginia Power’s icing out in 2021. Now the Charleston Dirty Birds, the organization is part of the independent Atlantic League. The Pioneer League and Pecos League are two larger independent league organizations operating in the American West, and could be the next to offer high level baseball at John Thurman Field.
For those curious about the pure developmental impact, Modesto’s park is generally the most difficult for hitters in the California League, which is still a comfortable space. Its high walls make it more challenging for sluggers, with it yielding not merely the most difficult home run environment in the Cal League, but in all of Low-A. Counter to the California League’s generally hitter-happy reputation, this has been impactful, though the curvature of its walls and their height do induce a lofty number of triples as a result. Inland Empire is a more extreme triple-friendly environment, but also affords a more measured offensive environment per Baseball America’s minor league park factors. While San Manuel Stadium grades as around 16 percent more homer-conducive over the past few seasons, its still well below the homer-happy rest of the league. In essence, when the 2026 Low-A numbers start rolling in, keep in mind that Seattle’s prospects will be playing more favorable locales to hit (or tougher ones to pitch) with greater regularity.
