The Yankees won a game, but lost a sweepstakes. 

Luis Castillo is being traded from the Reds to the Mariners, the teams announced Friday night. News of the deal broke shortly before the Yankees beat the Royals, 11-5, in The Bronx. 

Castillo has been seen as one of the jewels of the trade deadline, likely the top starter available for this stretch run and under team control for next year. The 29-year-old has a 2.86 ERA in 14 starts. 

The Mariners, who currently hold the second wild-card spot in the AL, are making a push and sent four minor leaguers — including three of their top five prospects as ranked by MLB Pipeline, infielder Noelvi Marte (No. 1), infielder Edwin Arroyo (No. 3) and righty Levi Stoudt (No. 5) — to Cincinnati for the righty. 

The Yankees have been in the market for starting pitching during a second half in which their rotation has grown holes. Luis Severino has been shut down since he left a July 13 start with a lat strain (though manager Aaron Boone said he hopes the righty can begin throwing again Monday); Jordan Montgomery has a 4.97 ERA in his past seven starts; Jameson Taillon sports a 5.36 ERA in his past 10 starts; and Nestor Cortes’ effectiveness has dipped in the second half. 

One of their first reinforcements, Domingo German, has not impressed in two outings. Behind Gerrit Cole, who allowed five runs in six innings Friday, there are plenty of questions. 

“I feel good about our rotation, and I feel really good about the guys we have in-house,” Boone said after the Yankees missed out on Castillo. “Guys are going to start moving and going different places. You never know what can happen over these next several hours — it’s going to be crazy, I’m sure. 

“There’ll be surprises. We may do things, we may not. But we know we have all the people in [the clubhouse] to do what we need to do.” 

With Castillo off the market, the Athletics’ Frankie Montas likely is the next best option, with the Pirates’ Jose Quintana in the mix, too. 

The Yankees witnessed Castillo’s brilliance two weeks ago, when he allowed one run in seven innings in The Bronx. Several Yankees praised the All-Star afterward, and there was speculation about whether Yankee Stadium would be his home in a few weeks. 

The speculation was premature. 

“If we get reinforcements or don’t,” Boone said, “we’ll be prepared either way.”