The Mariners made a major splash ahead of the Trade Deadline, acquiring Reds ace Luis Castillo in a blockbuster deal on Friday night.

Seattle sent four players to Cincinnati in return for Castillo, including three of its top five prospects. The return package included shortstops Noelvi Marte (the Mariners' No. 1 prospect) and Edwin Arroyo (No. 3), as well as right-handers Levi Stoudt (No. 5) and Andrew Moore.

“All of these kids, they're so much a part of what we've been building toward, and ultimately we knew that there would come a time where we'd feel like it was our time to take a step forward,” said Mariners president of baseball operations Jerry Dipoto. “This is why you build stronger, deep organizations. The talent that these guys bring to the table allowed us to go out and get what we thought was the top pitcher on the market, and really, what we thought was one of the better pitchers in baseball right now.”

The Mariners beat out several other teams to land Castillo. A dozen teams made their pitch for the right-hander, MLB.com's Mark Feinsand learned, with the Yankees "close," according to someone familiar with the talks. With Castillo’s regular turn to pitch lined up for Tuesday, Dipoto said that likely puts the righty on track to make his Seattle debut in the Bronx against the Yankees.

TRADE DETAILS
Mariners get: RHP Luis Castillo
Reds get: Minor League SS Noelvi Marte (Mariners' No. 1 prospect), Minor League SS Edwin Arroyo (No. 3), Minor League RHPs Levi Stoudt (No. 5) and Andrew Moore (unranked at time of trade)

Castillo, widely regarded as the top available pitcher on this year's trade market, is 4-4 with a 2.86 ERA in 14 starts. He made his second career All-Star appearance earlier this month in Los Angeles.

The 29-year-old Castillo had spent his entire career with Cincinnati to this point, racking up a 3.62 ERA in 137 career starts over six seasons. He is under team control through the 2023 season.

“He's one of the best pitchers in the game,” said Mariners manager Scott Servais. “Really established himself as a dominant starter in the National League. We've got a couple of his former teammates with us -- they know him very well and they speak very highly of his stuff, his competitiveness.”

The Castillo deal comes just four and a half months after Seattle acquired Jesse Winker and Eugenio Suárez from Cincinnati via trade on March 14. Dipoto acknowledged that the Mariners had discussed Castillo’s availability with the Reds at that time, as well as prior to the MLB work stoppage in December.

“He's the best. He's special and he's going to fit in great here,” said Winker, who played with Castillo in Cincinnati from 2017-21. “We have some outstanding pitchers here already, and he's just going to come in and be great. I'd say he's one of the best when he's out there doing his thing.”

The Mariners, who sit in the second AL Wild Card spot, boast a starting rotation that has a 3.68 ERA, seventh-best in the Majors -- but they could use some depth to spell some of their younger starters.

George Kirby, the club's breakout 24-year-old rookie, has thrown 96 innings between the Minors and Majors this season after pitching just 67 2/3 innings last year and missing all of 2020 due to the canceled Minor League season. Meanwhile, 25-year-old Logan Gilbert has tossed 123 innings this season -- quickly approaching his professional career high of 135 innings from '19.

Castillo provides another experienced arm in a rotation that also includes fellow veterans Robbie Ray, Marco Gonzales and Chris Flexen. Though Ray is the reigning AL Cy Young winner, he was tagged for four runs on five hits and four walks over just 2 2/3 innings in Friday’s 11-1 loss to the Astros, which raised his season ERA to 4.11.

The Mariners will discuss how to handle the rotation moving forward, though Dipoto noted that the club wants to find a way to keep Kirby involved through an entire 162-game season. Dipoto added that Seattle is still open to the idea of adding a bullpen arm, though he anticipates getting back both Diego Castillo and Ken Giles (both sidelined by right shoulder inflammation) shortly after Tuesday’s Trade Deadline.

Similarly, Dipoto is “open to opportunities” when it comes to potential additions on offense, but Kyle Lewis’ recent return coupled with Mitch Haniger’s impending return from a Grade 2 high right ankle sprain might be enough of a boost.

“We've got a chance to do something really big here this year,” Servais said. “You have got to step out and take a chance once in a while. If you ultimately want to get the reward, take a little risk -- and that's what we’ve got here.”