SEATTLE – The interest started last season. Discussions began in the days after the World Series , carried into the Major League Baseball general managers meetings in November and later into the winter meetings in December.

But the proposed trade in all of its iterations never quite found its way to the finish line … until now.

With two weeks until the opening of spring training, the Mariners are in the final stages of completing a trade to acquire St. Louis Cardinals All-Star infielder Brendan Donovan in a three-team deal involving the Tampa Bay Rays, sources with knowledge of the deal told the Seattle Times on Monday afternoon.

Per sources, the Mariners are sending a pair of former first-round picks — switch-pitcher Jurrangelo Cijntje and outfielder Tai Peete — and Competitive Balance Round B draft pick (68th overall) to the Cardinals.

Baseball America ranked Cijntje as the No. 7 prospect in the Mariners’ farm system and Peete No. 10.

Seattle is also sending 25-year-old third baseman Ben Williamson to the Rays. Tampa is giving up a draft pick and another prospect in the deal.

Donovan, entering his age-29 season in 2026, was a first-time All-Star in 2025, and he won a Gold Glove as a rookie in 2022.

In four seasons in St. Louis, Donovan has had a career slash line of .282/.361/.411 (. 772 OPS) with a 117 OPS+ (17% better than league average), 40 homers, 97 doubles and a 11.1 bWAR.

The framework of the deal had been finalized by mid-day Monday. Once medical reviews were completed and players were notified, the Mariners formally announced the trade Monday evening.

“It’s tough to imagine a better fit for our current team than Brendan,” Mariners president of baseball operations Jerry Dipoto said in a statement. “His combination of offensive skill, defensive versatility, consistency in performance, baseball instincts, and quality of character line up with what we value most.”

Donovan, who is in his second year of arbitration eligibility, agreed to a $5.8 million contract for 2026 with the Cardinals. The Mariners will have two total seasons of club control with Donovan becoming a free agent after the 2027 season.

He has a career on-base percentage of .361, making him a leading candidate to bat at the top of the Mariners lineup.

The top five hitters in the lineup — Donovan, Julio Rodríguez, Cal Raleigh, Josh Naylor and Randy Arozarena — have been all All-Star selections in the past two seasons.

Donovan’s 13% strikeout rate in 2025 was among the lowest in MLB, and his 119 wRC+ ranked fifth among regular MLB second basemen.

Per FanGraphs’ metrics, Donovan had a higher fWAR (2.9) in 2025 than Jorge Polanco (2.6), the middle-of-the-order slugger the Mariners lost to the New York Mets in free agency in December.

“Brendan brings a unique blend of elite top-of-the-lineup traits and versatility that makes him a perfect fit for our roster” Mariners general manager Justin Hollander said in a statement. “We are excited to welcome him to Seattle.”

Williamson was a second-round pick in the 2023 draft. An elite defensive third baseman, he made his MLB debut this season despite minimal time spent in the minor leagues. He played in 85 games, posting a .253/.294./.310 slash line with 13 doubles, a homer, 21 RBIs, 15 walks and 64 strikeouts in 295 plate appearances.

Cijntje, 22, taken with the 15th overall pick in the 2024 draft, was just in Seattle to participate in the Mariners’ FanFest event over the weekend. The Mariners recently announced a plan for Cijntje to focus on throwing right-handed exclusively in games, while still working on throwing from the left side in bullpens.

He was considered the third best pitching prospect in the organization behind lefty Kade Anderson and right-hander Ryan Sloan.

Peete, 20, was part of a trio of high school players selected in the first round of the 2023 draft, along with shortstop Colt Emerson and outfielder Jonny Farmelo.

Peete started his pro career as an infielder, but transitioned to the outfield this season. In 125 games with High-A Everett, Peete posted a .217/.288/.404 slash line with 24 doubles, four triples, 19 homers and 63 RBIs. But he also struck out 162 times.