The Mariners (39-36) scored twice in the final frame Friday for another late inning win in Kansas City. The Royals (39-35) have lost three in a row by just four runs combine.
Vargas had thrown 104 pitches when he gave up a double with two out in the top of the ninth of a 1-1 game. Manager Ned Yost made a mound visit, but turned back to the dugout after Vargas lobbied to stay in the game.
Seattle followed with an infield hit and Dustin Ackley's RBI single off Kansas City's starter to take a 2-1 lead.
The Royals had life when Jarrod Dyson drew a one-out walk in the bottom of the ninth, but Eric Hosmer hit into a game-ending double play.
Vargas took the loss despite allowing just two earned runs on ten hits in 8 2/3 innings.
Kansas City's offense gathered just three hits in the loss.
Alex Gordon's solo home run resulted in the only base runner to advance beyond first base against Seattle pitching.
The Royals will try to snap the losing skid in the series finale Sunday at 1:10pm.