It couldn't have gone any worse for the Orioles.
Cespedes hit a tying two-run homer off Matusz, then Baltimore made a pair of throwing mistakes in the 10th that allowed Eric Sogard to score the game-winner in the Athletics' 9-8 victory over the Orioles on Sunday.
"I think it just shows you a different chain when we give Jim a day," Showalter said after Baltimore's four-game winning streak ended. "I had to think about tomorrow, too."
The Orioles' bullpen blew a pair of two-run leads in the final four innings. Seth Smith hit a two-run home run off reliever Troy Patton in the seventh to erase a 6-4 deficit.
Chris Davis hit his team-leading ninth home run, a solo shot in the eighth that put Baltimore ahead 7-6. Machado added an RBI double in the ninth.
It didn't hold up.
Cespedes, activated from the disabled list before the game after being out with a strained muscle in his left hand, tied it with his homer. The A's won it in the 10th on Baltimore third baseman Manny Machado's throwing error on a bunt.
Sogard hit a leadoff single in the 10th and moved to second when reliever Pedro Strop (0-1) made a wide throw to second on Adam Rosales' bunt. Coco Crisp followed with a sacrifice bunt and Machado threw wildly past to shortstop J.
"Going in headfirst I couldn't really tell what was going on," Sogard said. "I was trying to read the crowd whether I was safe or out."
The loss was Baltimore's first on its longest road trip of the season and spoiled an otherwise stellar series by leadoff hitter Nate McLouth.
McLouth matched his career highs of four hits and four RBIs. In the four games against Oakland overall, he went 9 for 15 with one home run, seven runs scored and five RBIs.
Machado also had four hits for the Orioles.
Baltimore was trying for its first four-game sweep at the Coliseum since 1987. The Orioles lost for just the fourth time in 13 games.
Jerry Blevins (1-0) pitched one inning for the win.
Davis had a two-run double off Oakland starter Bartolo Colon in the fourth and later homered off Sean Doolittle.
Baltimore starter Miguel Gonzalez, who allowed only two baserunners through the first five innings, gave up four in the sixth.
"I tried to do too much," Gonzalez said. "A couple of pitches I was forcing it instead of just letting it go. That's a good hitting ballclub and I kept the ball down when I needed for the most part."
NOTES: Baltimore placed backup c Taylor Teagarden on the 15-day DL with a dislocated left thumb. ... LHP Zach Britton will make his first start this year when the Orioles begin a three-game series in Seattle. Britton, who was recalled from the minors on Thursday, is 16-14 in two seasons with Baltimore.