The Seattle Mariners, looking to end a postseason drought that stretches to 2001, acquired the best arm on the trade market Friday night in a deal for right-hander Luis Castillo of the Cincinnati Reds.

“He’s one of the best pitchers in the game — he’s really established himself as a dominant starter,” Mariners manager Scott Servais said. “We’ve got a chance to do something really big here this year. You have to step out and take a chance once in a while if you ultimately want to get the reward, take a little risk. Dominant starting pitcher, and I’m anxious to meet him.”

Minor leaguers Noelvi Marte, Levi Stoudt, Edwin Arroyo and Andrew Moore are headed to Cincinnati, the teams announced. Marte, a shortstop, is the highest rated of the group, with ESPN’s Kiley McDaniel ranking him the 12th-best prospect in baseball ahead of the season.

“We felt this was the best return we could get for Luis,” Reds general manager Nick Krall said.

The Mariners, led by star rookie Julio Rodriguez, are 54-47, 12 games behind the first-place Houston Astros in the AL West. They are in the second of three AL wild-card spots, a half-game in front of Tampa Bay (53-47) and two games ahead of Cleveland (51-48). Seattle won its final 14 games before the All-Star break, one short of the longest winning streak in team history and the best run by any club heading into the break since 1933. But the Mariners are 3-5 since, following an 11-1 loss at Houston on Friday night.

Now, they’ve added the best available arm ahead of the Tuesday trade deadline, one who will join an already-solid rotation that includes Robbie Ray and Logan Gilbert.

It’s a massive pickup for a Mariners organization that has not reached the postseason since 2001, the longest active drought among the four major North American pro sports leagues (MLB, NFL, NBA, NHL).

A 29-year-old right-hander, Castillo is 4-4 with a 2.86 ERA in 14 starts for the Reds this season, striking out 90 and walking 28 in 85 innings. His fastball averages 97 mph. He has a career 3.62 ERA in six seasons, all with Cincinnati.