The gentlemen who play for the Detroit Tigers, Milwaukee Brewers and New York Yankees are missing an excellent opportunity. One that may not come their way again.

At this moment, the Baltimore Orioles, who still lead the American League East by a half-game, are as exhausted and flat as they're likely to get. The Orioles, who lost their sixth game in their last nine tonight, 4-3, to the last-place Cleveland Indians, admit that they're drained from three weeks of dog-day survival.

The schedule maker, the weatherman, and the gods of baseball injury and luck have been doing overtime duty to conspire against the Orioles in recent days. Yet, thanks to the compliance of the Tigers, Brewers and Yankees--all of whom lost tonight--the Orioles find themselves unable to give away first place.

After a disgusting evening in Memorial Stadium, in which the home club scored three runs in the first inning for its ace, Scott McGregor, then went into a coma for the rest of the evening, Baltimore Manager Joe Altobelli sat in his office dissecting a most exasperating defeat.

"Detroit lost, too. Still in first," said a coach, sticking his head in Altobelli's office. Altobelli shook his head in disbelief and laughed.

This was an evening when, by all rights, the Orioles should have received a painful body blow. Gradually, the good July (19-7) signs that cheered the Orioles two weeks ago have been turning to ominous signs of August (3-6) gloom.

One game could hardly have held more bad signs for the Orioles, who lost their fourth in a row after a 20-6 binge. McGregor, trying to become the majors' first 15-game winner, saw his splendid record fall to 14-5 as Altobelli left him in the game despite a dramatic loss of effectiveness in the middle innings. The Indians scored one run in the fourth and fifth, then two in the sixth to win. The decisive Indian blows were a single by Andre Thornton, a game-tying hit-and-run triple by star rookie Julio Franco and a game-winning sacrifice fly by Ron Hassey.

To rub salt in Altobelli's slow-hook wound, reliever Sammy Stewart worked 3 1/3 shutout innings; since discovering a new curve to complement his slider and fast ball, Stewart has allowed four runs in 26 innings over nine games. He can't wait to get to the mound. "I'm full of confidence," said Stewart. "I've told Joe just to keep givin' me the ball, 'cause I can't pitch better than this."

Cleveland lefty Neal Heaton was seldom threatened after a rocky first inning when a Gorman Thomas error helped produce three unearned runs. After that first, Baltimore got only three hits and no runners past second base as Heaton threw 147 pitches in his first major league complete game. Like many a lefty before him, Heaton discovered that Baltimore's greatest weakness is a diet of slow southpaw curves and sliders down and in.

As a last twist of Orioles misfortune, Gary Roenicke clobbered a Heaton pitch with one out in the eighth that had game-tying-homer written on it, but the ball rocketed off the 14-foot high wall in left just 18 inches from the top.

While Heaton got a second wind, McGregor hit the wall in a hurry after getting the first 10 outs (on 10 hitters) with just 21 pitches. Thomas and Mike Fischlin had RBI singles in the fourth and fifth and, by the sixth, McGregor looked like he was pitching batting practice.

"Somebody once said to me when I was moping after losing, 'What's the matter with you? Why aren't you even allowed to have a bad day?' This was just one of my lousy days and I'm going to forget it," said McGregor, who, in his 14 previous starts had a 10-1 record, a 2.17 ERA and probably was the hottest pitcher in baseball. "My arm was just dead tonight. It's bound to happen. You just have to be realistic about it. Your arm gets to the point where it says, 'I can't do it tonight.' Maybe it needs some rest."

Baltimore got more bad news. Eddie Murray, who has missed the last four games with a sprained knee (the team has hit .214 without him), will probably not be able to start until Friday, if then. Murray pinch hit in the ninth, but managed only a weak check-swing ground out.

Right-hander Storm Davis, who had the worst game of his career Monday when Cleveland smashed him for eight runs, has further aggravated his stiff and tender elbow and will miss at least one turn. "It doesn't feel too good," said Davis. "I'll probably start again in 10 days. I probably shouldn't have even tried to pitch the third inning (Monday) . . . ."

In general, the Orioles are running on empty and admit it. After ending July with a long West Coast road trip, August has been brutal to them.

After the Hall of Fame game in Cooperstown came a doubleheader loss in Cleveland. After that, the Orioles came home, but, both Friday and Saturday, played rain-spattered games that didn't end until after 1:15 a.m. Next came a Sunday day game after a night game.

"We're dragging," said Ken Singleton. "That's why these're called the dog days."