BALTIMORE — A year ago Friday, on the final day of the 2011 regular season, the Boston Red Sox played here needing to win to keep their playoff hopes alive. The Orioles, who had lost 93 games, refused to let that happen.

The ripple effect from Baltimore’s 4-3 win on that warm Wednesday night has carried the teams on divergent paths, almost as reflective images of each other. In the 12 months since its loss, Boston has languished near the bottom of the American League East standings, and now the Red Sox are cast in the spoiler role against the wild-card-leading Orioles, who are seeking their first postseason appearance since 1997.

Baltimore took care of its business Friday, beating the Red Sox, 9-1. The Orioles pounded Boston’s starter, Aaron Cook, for six runs in the first inning, four on a grand slam by Ryan Flaherty. The scoring continued in the fifth, as four consecutive hits — three for extra bases — brought three more runs around. Baltimore had 11 hits in its first 24 at-bats.

That killed any real suspense, and the fans reveled in the role reversal from a year ago.

How Baltimore (90-67) got to this point — staying neck and neck with the Yankees for the division crown over the last month — could be traced to Game 162 a year ago, a win that still stings in Boston. The Red Sox blew a 3-2 lead in the ninth, then watched as the Tampa Bay Rays’ Evan Longoria hit a game-ending home run to beat the Yankees and snatch a trip to the postseason from Boston’s grasp. The Red Sox at one point had held a nine-game lead.