For at least a few more days--and maybe for longer than that--the champagne bottles will have to remain corked. On the verge of blasting their way right back into the A.L. East pennant race, the Red Sox lost a 5-4 heartbreaker at Detroit last night and fell three games behind the idle Yankees.

The Tigers took a 5-3 lead in the seventh with a four-run rally against Sox pitchers Don Aase and Jim Willoughby then held on for the win when reliever Steve Foucault quashed a ninth-inning Boston rally.

The Boston had jumped to a 3-0 lead early in the game on Carlton Fisk's second inning solo blast and a two-run, fourth inning rally helped out by some shoddy fielding. Motown's Jason Thompson responded in the bottom of the fourth with a one-run homer, his 30th of the year.

With Tiger starter Fernando Arroyo settling down to mow down Boston's awesome lineup, the game rested on the shoulders of the Sox pitching staff. As has happened so often in 1977, the mound crew did not come through.

Freddy Lynn launched an eleventh-hour rally by planting an Arroyo fastball in the right-field upper deck to lead off the ninth. But when Rick Burleson drew a walk off Arroyo with two outs, manager Ralph Houk made the call for Foucault, who silenced rookie Ted Cox's loud bat by forcing him into a game-ending pop-up.

Also surging Baltimore Orioles did manage to gain ground, though, downing the Toronto Blue Jays to close within 1 1/2 games of first. Oriole Lee May crunched a three-run homer and Bird pitcher Mike Flanagan hurled a six-hitter as Baltimore picked up a 7-1 victory, their 15th win in the last 19 games.

But the only certainty in the A.L. Eeast entering tonight's games is that there are ten games left, and that someone, in the next week and a half, will emerge as the winner.