The Seattle Mariners have officially promoted top pitching prospect Kade Anderson. The club announced in a press release that it has selected Anderson’s contract from Double-A Arkansas. Left-hander Jhonathan Diaz has been designated for assignment as the corresponding move.
Diaz’s DFA covers both the active and 40-man roster moves for Anderson’s looming promotion. Seattle has five days to either outright the 29-year-old to the minors or release him.
The Mariners are hanging on to the postseason chase by a thread. They are four games back of the Houston Astros in the American League West and three games back of a Wild Card spot. FanGraphs gives Seattle a 33.3% chance of making the postseason.
Anderson’s debut will be the most anticipated since Paul Skenes’ two years ago. He’ll face the Chicago Cubs at T-Mobile Park, with a first-pitch time of 7:15 p.m. ET (4:15 p.m. PT).
Mariners DFA Jhonathan Diaz as Kade Anderson Corresponding Move
GettyJhonathan Diaz has been DFA’d by the Mariners for the third time since 2025. (Photo by Alika Jenner/Getty Images)
Jhonathan Diaz had been an up-and-down player for the Mariners the past three seasons. The club selected him from Triple-A on August 19 after spending most of the season with Triple-A Tacoma.
He pitched the next day, logging 1.1 innings in the series finale against the Milwaukee Brewers. That serves as his only MLB appearances this season.
Once a prospect for the Boston Red Sox, he’s bounced around two different AL West teams in his career. He previously pitched for the Los Angeles Angels before the Mariners signed him as a minor league free agent in 2024.
Diaz pitched in seven games with Seattle the past three years, totaling 12.1 innings. The left-hander has burned his last minor league option this season, so the club is cutting ties.
This move marks the third time that Diaz has been DFA’d by the Mariners since 2025. He elected free agency the previous two times Seattle attempted to outright him to the minors.
Mariners Top Prospect Kade Anderson Makes MLB Debut vs. Cubs
GettyThe Kade Anderson era in Seattle starts, as the club announced his promotion. (Photo by Al Bello/Getty Images)
Kade Anderson will make his long-anticipated MLB debut against the Chicago Cubs on August 22. This comes as the team scratched right-hander Bryan Woo from that start.
The left-hander was the No. 3 overall pick in the 2025 MLB Draft. He was the College World Series’ Most Outstanding Player in LSU’s National Championship run and was considered the most pro-ready pitcher in a draft class with great college pitching. He’ll be the first player from the 2025 draft to make his MLB debut.
In 18 starts with Arkansas, Anderson has a 1.06 ERA across 93.1 innings. He’s been downright dominant at that level, punching out 40.5% of opposing hitters. It was only a matter of time before Seattle would promote the 22-year-old.
The Mariners will get a preview of what their future rotation will look like. Anderson, along with right-hander Ryan Sloan, are two of the best pitching prospects in baseball.
It’s unclear how long the Mariners will need Anderson in the rotation. Manager Dan Wilson offered no clarity as to when Woo may get reslotted into the rotation, although he was optimistic the 26-year-old would avoid a stint on the injured list.
Depending on how Anderson looks in his first MLB stint, that could affect the Mariners’ offseason plans. Logan Gilbert and George Kirby will both be free agents following the 2027 season, so the club could try to get a return for one of the two pitchers and improve their offense.
Mariners Cut 6-Year MLB Pitcher to Make Room for Kade Anderson