FINAL GRADES: Luis Castillo's Veteran Presence Elevated Seattle Mariners Rotation
The Seattle Mariners starting rotation was arguably the best in baseball this season.
Four of the Mariners' five starting pitchers were all drafted and developed by the organization. Just one starter wasn't home grown.
That pitcher was three-time All-Star and former Cincinnati Red Luis Castillo.
Castillo entered the season and played most of the year as the No. 1 pitcher in Seattle's rotation. Logan Gilbert seemed to take that spot in perception if nothing else by the end of the year. But that was more to Gilbert's elite season than anything bad shown by Castillo,
Several of the other pitchers in the rotation also spoke about how Castillo has helped them this season.
The eighth-year starter's campaign came to an unceremonious end after he missed the last 19 days of the year with a grade-2 hamstring strain.
But Castillo continued to prove himself as a valuable starting pitcher in the league. And that bodes well if the Mariners do end up having to trade one of their hurlers.
Luis Castillo by the numbers
Games started: 30
Pitching stats: 3.64 ERA, 30 appearances (30 starts), 11-12 record, 175.1 innings pitched, 175 strikeouts, 1.17 WHIP, 18 QS, .238 opp. BA, 1.8 WAR
Advanced pitching stats: 3.94 xERA, .247 xBA, 31% Chase, 25.9% Whiff, 3.91 FIP, 8.98 K/9, 74.9% LOB
What I liked
Castillo didn't show any signs of slowing down in his age-31 season.
After having a disappointing June (5.13 ERA), he bounced back in July and had a 1.99 ERA in five starts.
Castillo came back down to Earth toward the end of the year and posted ERA totals of 4.66 in August (five starts) and 3.60 in September (two starts), but he showed the ability to adapt at the midpoint of the season.
Castillo successfully modified his changeup to create more movement. The fact that he was able to make that adjustment is a good testament to the versatility of Castillo.
Castillo has a four-pitch arsenal of a four-seamer, slider, sinker and his aforementioned changeup, according to Baseball Savant. And his low-quarter arm-slot, which has been effective his whole career, continued to be a problem for batters in 2024.
Luis Castillo, Wicked 89mph Changeup. 👌 pic.twitter.com/oZ0noV2yjb
— Rob Friedman (@PitchingNinja) August 7, 2024
Seattle will likely change the order of the rotation in 2025 even if they don't trade a starter. Castillo's proven ability to adjust will mean that wherever Castillo is in the rotation, he'll be just fine.
Best game
Castillo had several games with over seven strikeouts but his best outing probably came toward the beginning of the season.
In a 7-0 Mariners win against the Colorado Rockies on April 20, Castillo shutout the Colorado offense in seven innings of work.
He let up just two hits and walked one batter while striking out nine.
Luis Castillo's 9th K...and Strikes his K Pose. pic.twitter.com/1RnXqTRUdF
— Rob Friedman (@PitchingNinja) April 21, 2024
Castillo had a nearly identical outing two starts later on April 30 in a 3-2 victory against the Atlanta Braves when he also pitched seven innings and struck out seven batters. He allowed just three hits and walked one in that victory.
Future prospects
There's been a lot of rumors over whether or not Seattle will trade a starting pitcher in the offseason in an effort to get elite bats.
In an article published by the Seattle TImes' Adam Jude, Castillo is the "least likely" of the five starters to be moved according to one industry source.
Castillo has three more years left on his contract with a vesting option for 2028. He's set to earn $24.15 million every single year in 2025-27. He also has a no-trade clause, meaning that any deal that would involve him needs his seal of approval.
Castillo is a respected presence in the locker room among players and coaching staff alike. He also proved in 2025 that he still is one of the better starters in the league.
Barring a major drop-off in 2025, there's no reason for the Mariners to move Castillo.
Final grade: B
B: Castillo was a good pitcher by all metrics this season. At his best, he showed the usual elite stuff that's been present since his time in the National League.
But his up-and-down trajectory month-to-month makes it impossible to give any more than a "B" here.
There's an argument to be had that the move to trade for Castillo and his subsequent contract extension is the best move President of Baseball Operations Jerry Dipoto has made during his time with Seattle.
Aside from his on-field acumen, Castillo's aforementioned versatility and team-first mindset allows the Mariners the flexibility to reorganize the rotation however they see fit.
Gilbert will likely be the team's No. 1 starter next season and there's a good chance Castillo gets bumped down to No. 4 in the order behind Bryce Miller and George Kirby, as well.
But Castillo clearly has at least a couple more solid seasons left and will continue to play a big part in Seattle's success going forward.
Related Stories on Seattle Mariners
FINAL GRADES ON GEORGE KIRBY: The Seattle Mariners starting rotation was bolstered by the elite command displayed by George Kirby, who had one of the most impressive streaks of the season in 2024. CLICK HERE
FINAL GRADES ON BRYAN WOO: Bryan Woo's growth was a massive factor in the Seattle Mariners having the best starting rotation in baseball this season. CLICK HERE
FINAL GRADES ON JOSH ROJAS: Josh Rojas' defense and offense was on two opposite ends of the spectrum, but it might have been enough to earn him a longer stint with the Seattle Mariners. CLICK HERE
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