McLouth stole second base on the third pitch. J.J. Hardy then drove him in by grounding a hard single up the middle.
The O's had consecutive singles to start the sixth before Adam Jones' sacrifice fly made it 2-1. McLouth added an RBI single in the seventh and had a sac fly in the ninth, when the Orioles scored twice off Rangers closer Joe Nathan.
Jim Johnson, who set an Orioles record with 51 saves, allowed a walk and two hits in the ninth, including a two-out pinch single by 19-year-old Jurickson Profar that loaded the bases, before David Murphy's season-ending flyball caught by McLouth in left field.
"Me and my teammates and the Rangers' fans, I don't think we all thought that it would end this early," Darvish said through a translator. "I mean, right now, no. I don't even know what I'm supposed to do tomorrow."
Darvish won 16 games in his rookie season in the majors, after the Rangers committed more than $107 million last winter to acquire Japan's best pitcher. The 26-year-old right-hander was 8-2 with a 1.38 ERA in 11 postseason starts in Japan the past six seasons.
Showalter managed in Texas for four years before being fired and replaced by Washington after the 2006 season. Darren O'Day, the sidewinder who pitched two scoreless innings in relief of Saunders, is one of seven former Rangers players now with Baltimore — and advancing in the playoffs.
"I have a lot of respect for the Texas Rangers and what they've done these past few years and the opportunity they gave me," said O'Day. "It was more satisfying just to make the playoffs with this group of guys. People thought we'd be making tee times right now."
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