Only five days ago, Baltimore pitcher Nelson Briles sprinted toward the Fenway Park mound in Boston, carrying a bag of batting practice baseballs in his arms.

Briles tripped, fell on his face and spilled 100 balls across the infield. As Briles crawled around in the dirt, collecting balls and acting as if nothing had happened, the 20,000 early arrivals howled with delight.

"He does that once in every park," said Oriole shortstop Mark Belanger.

"But he agreed to do it two days in a row so my brother could see it."

Back in the O's dugout the grimy Briles was accepting congratulations.

"Not as good a fall today," evaluated Briles, "but better ball distribution."

"Here come the scores," pitching coach Rabbit Miller said breathlessly, pretending to look into the bleachers. "Here they are: 7.8, 7.9, a perfect 8.0. And, what's this? A miserable 3.1"

"That Russian judge has never liked me," growled Briles, as he trudged to the clubhouse to change to his game uniform.

Last weekend the sun shown on a Baltimore team that had won 18 of 20 games. Baseball was more than fun; it was life at the top.

"Someday I want (Jim) Palmer to manage this team," said Bird Manager Earl Weaver, his feet propped up on the steps of the Fenway dugout, "so I relieve a pitcher who's just like him."

The Orioles twittered. For years pitching coach Bamberger would go to the bill and tell Palmer the same thing: "You're no bending your back or following through. That's why you're wild high."

And each time Palmer would have the same sarcastic two-word answer, the first word of which was "No." And every time Bamberger's head would snap back like it had been slapped.

"George'd come back to the dugout," laughed Weaver, "and he's say, 'Well, he said it again.'"

"At least," broke in Palmer, joining the mutual harrassment, "I'll never go out to a pitcher after he's thrown six high balls in a row and say, 'Bounce one.'"

"Maybe not," said Weaver, "but you'll move the outfielders plenty. I gotta move our outfielders 10 steps to the right so when you move 'em back five steps to the left, they'll end up in the right place."

All this was when the perky Birds were pecking at the edges of a pennant race.

Last night at 6:01 p.m. the Birds - losers of their last seven straight - were taking batting practice. "Where's the music?" yelled one Oriole, aware that the public address rock 'n' roll was supposed to start at precisely 6 p.m.

"We're not in a good mood," said Belanger, the Oriole captain. "Things change fast in this game, too fast. There's no time to let up, to relax. No time to enjoy it. When you're winning, you have to keep winning. When you're losing, you better start winning in a hurry."

Even when the Orioles gave up 24 runs in the first five innings of Monday's game in Toronto, they kept their reasonably good spirits. In baseball, one-run defeats hurt for days, slaughters are forgotten in minutes.

Mike Flanagan, the starter who had given up six runs in an inning, confronted centerfielder Larry Harlow, who had allowed five scores in 2/3rds of an inning of emergency relief.

"What this proves," said Flanagan to Harlow, is that you can't pitch with seven years off between starts."

Catcher Elrod Hendricks, who had shut out the Blue Jays for 2 2/3 innings, was insisting that he had not thrown pitches that had bubble gum attached to them. Other Birds said he had. "They were just too exhausted from running the bases to hit my changeups," explained Hendricks.

Even Oriole announcer Chuck Thompson was in the act, proud of the presence of mind that had prompted him - in the midst of the Hendricks-for-Harlow mound conference - to say on the air to fellow announcer Bill O'Donnell, "Bill, if anyone knocks on the door of the booth, don't answer."

The next two days, however, brought three more defeats, two by one run. The winning streak was forgotten, its month-long mood of buoyancy shattered by a few days of Toronto mischief.

Only Weaver, whose long experience and natural disinelination to panic, could manage a half-smile yesterday.

"If we don't win a couple of them (four) games against Boston," he said, eyes twinkling, "the good people of Baltimore might think we're out of the race. I wouldn't want them to lose the faith."

Baltimore has been reasonably immune to that Oriole faith for some years.

"If we just pretend Boston isn't in the league anymore," said Weaver, "we still got a hell of a race." A race for second place.

The delights of contending for runner-up are small, even for the Orioles, who deserve plaudits if they even approach last season's 97 victories.

The casualty of Boston's lead is not only attendance, but joy. Four days ago, victory enabled the Orioles to laugh and enjoy their candor.

At that time, Weaver regaled his players with an imitation of one of his outfielders running in and having a liner whistle past his ear. "Fielding an air ball," Weaver called it.

It wouldn't be funny if that innocent mimicry found its way into the Baltimore dugout these days.

"You don't have to worry," Palmer said to Weaver. "I'll never have your job. I'm going to die with my hair still brown."

"How did Dave Leonard turn out so good," answered Weaver, referring to one of Palmer's closest boyhood friends, "and look what happened to you."

But that was four days ago when Oriole baseball was shutout pitching, Briles in a cloud of dust and Russian judges in the bleachers. That was before Elrod Hendricks unveiled his bubble gum changeup.

Last night, at the hour when Briles' pratfall sometimes occurs, it was raining on Memorial Stadium. Perhaps the plucky Orioles deserved better, if their sport rewarded only intelligent effort and ignored talent.

But the Birds know the strict rules of the game: Laugh today, for in baseball, tomorrow always comes too soon.