The Orioles' bullpen began the day with the third-lowest ERA in the majors at 2.38, but it couldn't protect a one-run lead today.
Darren O'Day gave up the tying run in the seventh on back-to-back doubles by Eric Hosmer and Humberto Quintero with one out. Hosmer's ball didn't leave the infield. It rolled up the third base line and stopped short of the bag.
Mitch Maier followed with a single, but Quintero held at second, unsure if the ball would drop in left field. O'Day struck out the next two batters.
Pedro Strop entered in the eighth, bringing a streak of 13 straight scoreless appearances over 14 2/3 innings. He allowed one run and three hits, and walked a batter.
Hosmer's bloop single into left field with the bases loaded and one out gave Kansas City a 4-3 lead.
Wei-Yin Chen turned in his fifth quality start, allowing two runs and six hits in six innings. But he won't get the win.
The Orioles are 22-2 when the rotation has a quality start.
Down on the farm, Zach Britton has been charged with two unearned runs after Mark Reynolds committed an error. Reynolds, starting at third base, struck out in his first at-bat.
Britton has allowed three hits, walked one and struck out five in two innings.
Dylan Bundy, making his first start at Single-A Frederick, gave up his first two earned runs as a pro on Travis Shaw's two-run homer in the fourth inning. Bundy hadn't permitted an earned run in 33 innings.