Right-hander Mason Black is set for his Royals debut on Sunday. He’ll be joined by catcher Elias Diaz, who had his contract selected by the club. Right-hander Mitch Spence and infielder Tyler Tolbert were optioned to make room for Black and Diaz, the team announced. Right-hander James McArthur was moved to the 60-day IL to clear a 40-man spot for Diaz.
Kansas City acquired Black from the Giants for right-hander Logan Martin in November. Black had some fanfare when he first came up with San Francisco in 2024, but he failed to provide consistent results. The righty finished his Giants tenure with a 6.47 ERA in 10 games over the past two seasons.
The 26-year-old Black was almost exclusively used as a starter in San Francisco, but he’s moved to a relief role with Kansas City. He has a 3.86 ERA over seven appearances at Triple-A this year. Black locked down the first two saves of his professional career with Omaha. Despite the full-time move to the bullpen, Black has just a 12.5% strikeout rate so far. Often, those numbers improve when starters make the change to relief work, as their stuff usually plays up in shorter outings.
Spence joined the organization in February following a trade from the Athletics. He didn’t break camp with the team, but came up in early April when right-hander Luinder Avila was sent down. Spence was tagged for six earned runs across four innings in mop-up duty against the Yankees on Saturday. He’ll head back to Triple-A after just the one big-league appearance.
Tolbert made the team out of camp, beating out Drew Waters for a roster spot. Michael Massey‘s calf strain in MLB Spring Training helped Tolbert and Nick Loftin earn roster spots. Loftin was sent down when Massey returned. Now, it’s Tolbert’s turn. He appeared in eight games with the Royals, with the majority of his work coming as a pinch runner or defensive replacement. Tolbert managed a hit in five plate appearances.
McArthur missed the entire 2025 season after undergoing elbow surgery. He opened the 2026 campaign on the 15-day IL due to elbow inflammation. His return timeline is uncertain. The righty was a key member of Kansas City’s late-inning group when he last pitched, recording 18 saves in 2024.
Photo courtesy of Scott Sewell, Imagn Images
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