BALTIMORE -- Orioles manager Buck Showalter can only hope the impressive starting pitching he's seen recently will continue next April.
It was the second time in three days that Detroit was swept in a doubleheader; the Cleveland Indians did it Wednesday. The Tigers (80-80) have lost five straight and must win at least once this weekend to avoid a losing season.
"That's what's going to have to happen for us to get where we want to go," Showalter said. "It [revolves] around pitching ... and making leads matter late in games. It's been impressive and we hope it carries over."
Robert Andino had four hits in the nightcap for the Orioles, who improved to 33-22 since Showalter made his debut on Aug. 3. With its first doubleheader sweep since June 2006, Baltimore reached the 65-win mark -- one more than it had last year.
"You're always looking for improvement," Showalter said. "When you step back at the end of the year, you want to feel like you're in a little better shape than you were last year at the end of the season."
Guthrie (11-14) struck out five, walked one and permitted only one runner past first base. The right-hander went 8-4 with a 2.75 ERA in 14 starts after the All-Star break.
Rick Porcello (10-12) gave up two runs and 12 hits in 6 1/3 innings. Bidding to win his sixth straight decision, Porcello fell behind when Markakis opened the third by driving an 0-2 pitch into the right-field seats.
While the Orioles are sprinting to the finish, the Tigers are limping toward the end of a disappointing season.
"It's not good when you lose them two at a time, like we did in Cleveland and here," manager Jim Leyland said. "But you got to keep battling, keep scratching and clawing."
Kelly, who also homered in the opener, said, "It's tough. You never want to lose a bunch in a row. We've got to find a way to battle back these last two games."
The first game was a makeup of Thursday night's rainout. ... Orioles second baseman Brian Roberts missed both games with headaches. ... Detroit catcher Gerald Laird left the nightcap with a bruised left shoulder. Leyland does not expect Laird to play again this season.