With less than four weeks until the Seattle Mariners open their season on March 26, activities are intensifying in Peoria, Arizona. Although the Mariners stand at 3-5 in the Cactus League, their pitching staff has struggled, allowing 62 runs, the third-most among participating teams. Despite this rough start, the main focus remains on player development and individual performances rather than the current win-loss record as the team gears up for the regular season.
Among the stories unfolding is the professional debut of top prospect Kade Anderson and an encouraging velocity update from veteran pitcher Luis Castillo.
Kade Anderson Impresses in Professional Debut Despite Early Challenges
After missing much of the 2025 minor league season following his selection as the No. 3 draft pick, 21-year-old left-hander Kade Anderson made his pro debut for the Mariners on Saturday against the San Diego Padres. Anderson quickly caught attention by striking out all three batters in the first inning, showcasing his swing-and-miss potential early on.
Kade Anderson’s 3Ks in the 1st. pic.twitter.com/LFi4ZNTrEe — Rob Friedman (@PitchingNinja) February 28, 2026
Despite this strong start, Anderson faced adversity right away. An infield single and a walk extended the inning, and he was replaced in the second inning after surrendering hard-hit singles, including a 102.3 mph hit by Freddy Fermin and an even harder 105.3 mph double by Jake Cronenworth. He ultimately was charged with two runs.
Anderson threw a total of 30 pitches, with his fastball averaging 93.8 mph and registering a peak speed of 94.9 mph. His fastball also stood out for its movement, featuring 17 inches of vertical break and five inches of horizontal movement. Additionally, his changeup generated three swinging strikes on three swings, a promising sign for his ability to disrupt hitters.
Right-hander Ryan Sloan, ranked as the No. 33 prospect by MLB Pipeline, is set to pitch in Sunday’s exhibition game against the Texas Rangers, following Anderson’s debut.
Luis Castillo Shows Encouraging Increase in Fastball Velocity
Luis Castillo, the Mariners’ 33-year-old starting pitcher, encountered difficulties during his Cactus League debut on Friday against the Arizona Diamondbacks, allowing three runs on four hits while recording only four outs. However, Castillo’s fastball velocity offered a bright spot, consistently reaching around 95.0 mph with a top speed of 96.3 mph.
This performance marks a significant improvement over last spring, when Castillo’s fastball failed to surpass 94 mph. In the 2025 regular season, his four-seam fastball averaged 95.0 mph, so reaching that mark during spring training already signals positive progress toward his offseason goal of regaining lost velocity.
Castillo has experienced a decline over recent years, dropping 2.1 mph in average fastball speed since 2022, and his strikeout rate slid to a career-low 8.1 strikeouts per nine innings in 2025. Reclaiming even part of that velocity could help him reverse this downward trend and improve his effectiveness on the mound.
Injury Updates Affecting Key Mariners Prospects and Veterans
Spring training has brought some injury setbacks for the Mariners. Left-hander Bryce Miller is dealing with inflammation in his left oblique, which will sideline him for his next Cactus League start. Miller had shown promise in his debut on Thursday, generating high optimism among the team before the injury surfaced.
A loose timeline for Bryce Miller (left side oblique inflammation), per Justin Hollander…• No activity through the weekend• Light catch play for 5 days after• Re-evaluation 7 days from now — Daniel Kramer (@DKramer_) February 28, 2026
Outfield prospect Victor Labrada is also experiencing oblique issues after a strain sustained while working in the batting cage. Mariners General Manager Justin Hollander expects Labrada to be out for an extended period. This is a significant setback for the 26-year-old, who ranked No. 27 on the Mariners’ prospect list last season and was projected to reach the major leagues in 2026.
Meanwhile, shortstop J.P. Crawford is progressing from a right shoulder injury that has kept him out of action. He is slated to return to the lineup as designated hitter on Tuesday, with a possible return to shortstop by March 8. Until then, Colt Emerson will handle shortstop duties before shifting to third base or second base once Crawford returns.
Mariners Maintain Focus on Player Development and Roster Adjustments
Although spring training records such as 3-5 and a struggling pitching staff might cause concern, Seattle‘s main priorities remain honing player skills and managing injuries as the regular season approaches. The impressive debut of Kade Anderson and Luis Castillo’s velocity improvements signal promise for the Mariners’ pitching depth ahead.
Despite setbacks with Bryce Miller and Victor Labrada’s injuries, the team is carefully monitoring recovery timelines to ensure readiness. J.P. Crawford’s return will provide stability in the infield, emphasizing the need for versatile players like Colt Emerson to adapt in the meantime. All eyes will be on how these developments influence Seattle’s rotation and roster stability as the season opener nears.
Kade Anderson's 3Ks in the 1st. pic.twitter.com/LFi4ZNTrEe
— Rob Friedman (@PitchingNinja) February 28, 2026
Ryan Sloan is listed to pitching in tomorrow's game against the Rangers. Logan Gilbert to start.
— Shannon Drayer (@shannondrayer) February 28, 2026
A loose timeline for Bryce Miller (left side oblique inflammation), per Justin Hollander…
• No activity through the weekend
• Light catch play for 5 days after
• Re-evaluation 7 days from now— Daniel Kramer (@DKramer_) February 28, 2026
