The defeat, which saw starter Scott Feldman last seven outs and allow eight runs in his worst outing of the season, featured a pair of homers from middle-of-the-order bats Adam Jones and Chris Davis, who extended his Major League-leading total to 53.
"It's unfortunate," Orioles manager Buck Showalter said of Feldman, who had allowed eight earned runs total in his previous five starts. "You're facing, won-loss record, the best team in the league and there's a fine line. You've seen it against them. He makes a little bit better level of pitches, he's effective. Fortunately, we've seen him pitch a lot better, and tonight wasn't one of those."
A free agent at season's end, Feldman retired leadoff man Jacoby Ellsbury before allowing the next five Boston batters to reach base. That first inning, which got the Orioles bullpen going, saw Feldman tagged for five runs, including Daniel Nava's three-run shot on a 75-mph curveball.
"Just wasn't very good," said Feldman, who said he would like to return to Baltimore next year. "It seemed like I made lot of mistakes, behind in the count, and they hit them. Any time I made a mistake, they pretty much put the good part of the bat on it and hit it pretty well."
After a 1-2-3 second inning, Feldman got into trouble again in the third with a pair of one-out singles, but he got a break on the home run reversal call on Jarrod Saltalamacchia's ball -- which didn't clear the grounds crew shed in right field -- that was ruled to be an RBI double.
Still, it was enough for Showalter to insert lefty Zach Britton, who allowed two inherited runs to score to push the Red Sox lead to eight. It also marked the second-shortest outing of Feldman's career.
"Scott would be the first to tell you [he was not his best] tonight, but he's the guy we felt like could come in here and give us a chance to win games, and he did," Showalter said of Feldman, who was acquired in a midseason trade with the Cubs. "He's a guy who, I guarantee if there was another outing, you wouldn't want to be facing him. He's a pro. It hurts to see him finish the season like that, but knowing Scott, it will drive him even more.
"He's going to be 31 years old next year and he's a guy whose statistics have come over to the American League just like they were in the National League. He's going to be somebody that people are going to want, including us. He's solid. Tonight wasn't the night, though, and that's frustrating for him. I would have liked for him to finish the season on a note that's more indicative of how he's pitched this year."
Jones put the Orioles on the board against Red Sox starter Clay Buchholz, connecting for a two-out, two-run homer in the third. Davis crushed the first pitch he saw one out into the sixth for his 53rd homer, bringing his RBI total to an incredible 138 on the year. He is the first player to reach both those marks since Alex Rodriguez in 2007.
Davis, who eclipsed the club record earlier this month, has hit 28 homers at Camden Yards, which is a new home record for the franchise. He passes Hall of Famer Frank Robinson, who hit 27 at Memorial Stadium in 1966. But the pair of homers fell far short on a night in which Boston went deep three times and totaled 16 hits.
"They came out swinging the bats," shortstop J.J. Hardy said of a Boston team that secured home-field advantage in the AL Division Series. "They hit some good pitches, put up a lot of runs. It wasn't we weren't trying, they just hit some good pitches."
Britton served as a solid bridge to the rest of the bullpen, tossing 3 2/3 scoreless innings before turning the ball over to right-hander Steve Johnson to start the seventh.
Lefty Mike Belfiore made his Major League debut two outs into the eighth inning and served up a three-run homer to David Ortiz, the first batter he faced. Two of those runs were charged to Johnson. Belfiore also allowed a solo homer to Jonny Gomes in the ninth.
"It would have been nice to finish up a little stronger heading to the offseason, coming off a good game," Feldman said. "But the bottom line is, everybody in here wanted to make the playoffs and we didn't do it. So hopefully next year we'll get in there."