Daniel Nava and David Ortiz each slugged a three-run homer, as Boston crushed Baltimore, 12-3, in the opener of a three- game season-ending series from Camden Yards.
Stephen Drew added two hits and drove in three, with Jonny Gomes hitting a solo shot for the Red Sox, who have taken five of seven.
Clay Buchholz (12-1) capped his season with seven effective innings, allowing seven hits and three runs while fanning four.
"It's a good stepping stone," Buchholz said. "I'm just glad the team could score all those runs. There wasn't a whole lot of stress in the outing today."
Adam Jones launched a two-run shot and Chris Davis contributed a homer for the Orioles, who have dropped seven of their last nine.
Scott Feldman (5-6) was tagged in defeat for eight hits and as many runs over just 2 1/3 frames.
"It would've been nice to finish up a little stronger heading to the offseason coming off a good game," Feldman said. "But the bottom line is, we all, everybody in here, wanted to make the playoffs and we didn't do it. Hopefully next year we'll get in there."
Boston took control early on, picking up five runs in the first inning on Napoli's RBI double, followed by Nava's three-run blast and a run-scoring triple by Drew.
The visitors went up 8-0 in the third courtesy of an RBI single from Jarrod Saltalamacchia and two-run hit by Drew.
Baltimore finally countered in the home half as Brian Roberts singled with one out and scored on Jones' two-out, two-run shot to center.
Davis added to his franchise record by hitting number 53 in the bottom of the sixth to draw the O's within five, but the Sox assumed an eight-run margin in the eighth on a three-run homer by Ortiz.
Gomes began the ninth with a solo shot to increase Boston's advantage to nine and capped the scoring.
Baltimore still owns a 9-8 edge in the season series ... Ortiz reached the 30- homer plateau for the seventh time in his career and for the first time since going deep 32 times in 2010 ... Gomes totaled three hits and scored three times, while Dustin Pedroia also hit safely three times and crossed home twice for the Red Sox.