When baseball holds its All-Star Game here Sunday night, it will bear little resemblance to any of its 51 forebears.

This affair is neither a reopening day nor an All-Star Game.

It is baseball's public apology.

And no one knows yet whether it will be accepted.

Normally, the folks in the seats watch the players on the field.

This time, it's the players who will be watching the fans.

"Whatever damage the game's suffered, it's been done and can't be undone," said Mike Schmidt, the National League's most valuable player last season. "Now, we have to start the rehabilitiation."

For days, this midsummer nightmare of a game, already postponed twice by baseball's 50-day strike, has loomed as another potential disaster for the sport. Everything that could go wrong seemed on the verge of doing so.

However, in just the last few hours, many of those bleak omens have changed.

Is it possible that baseball's luck is turning?

For two days, the game's hot rumor was that the umpires would boycott the All-Star Game, then begin a strike on Monday over back-pay grievances.

But Richie Phillips, the counsel for the Major League Umpires Association, told his men that he would not allow them to strike the All-Star Game, according to the Associated Press. Phillips said that the umpires would hold a meeting here.

Next, the rains arrived -- n a deluge Friday, then steadily today.

Could there be a more fitting, and miserable, coup de grace than the rainout of a makeshif All-Star Game that had already been struck out twice?

Baseball brass mumbled about a makeup date on Aug. 20; the moguls will get the cash from this baby if they have to play it on Thanksgiving.

But an All-Star washout would tangle an already ludicrous schedule, one that necessitated that four games on the 20th be moved up to the 17th.

Then, lo and behold, the weatherman changed it's mind and vowed that the rains woudl abate before the bewitching hour of 8:30 p.m., when NBC (WRC-TV-4 in Washington) introduces a new sort of second season.

"Split season fever, catch it," said a makeshift sign in the commissioner's suite here this afternoon.

The next worry, in this sport that has had a migraine for nearly two months, was that the Cleveland Browns Pittsburgh Steelers exhibition game at Municipal Stadium this evening would leave the grass field a chewed-up quagmire.

"Maybe we can ask them to call a lot of sideline plays so that we can still find the middle of the field and second base," said Jim Frey, American League manager.

However, according to Indian Manager Dave Garcia, the stadium turf is so fresh and unused that no one game can do significant damage. Time will tell on that one. After all, this is the drafty, cold and ugly-when-empty park that ballplayers call "The Dungeon" and "The Mistake by the Lake."

Finally, it was speculated that, because of the air traffic controllers strike, various players and dignitaries would have to hitchhike to get to this city on the shores of a very polluted lake.

So far the only absentee has been the NL's starting pitcher, Fernando Valenzuela (9-4, 2.45 ERA) of Los Angeles, who missed a mass press conference because of a fight cancellation.Presumably the southpaw, whom National League Manager Dallas Green respectfully calls "Mr. Valenzuela from the State of Mexico," will arrive in time to match his soft screwballs against the hard sliders of American League starter Jack Morris (9-3, 2.56) of Detroit.

Actually, this 52nd All-Star Game has nice possiblities, if the rains stop and the field isn't a mire.

For once, and some would say for the only time, the players are, as a group, taking the game extremely seriously.

"I think you'll see the best baseball ever played during the rest of this season, starting with the All-Star Game," said Baltimore's Ken Singleton who, despite his distinguished career, is starting his first All-Star Game. "We (players) have a lot to prove. If any player on any team doesn't hustle the rest of this year, a strange thing's gonna happen. He may hear himself being chewed up from both dugouts. We know we're being judged."

First evidence of this quasiofficial union policy is the amazing fact that 100 percent of the 60 players chosen for these squads will actually be in Cleveland. For once, no phony injuries. No yawns. No sulking by players who were insulking by players who were insulted not to be starters and refused to show for bench duty, like Garry Templeton of St. Louis who last year called the game a joke, then begged out. Even New York's Rich (Goose) Grossage, who has a stiff shoulder and has been replaced by teammate Ron Davis, has proved the legitimacy of his injury by promising that he will be here for the game, although he can't play.

Even the game itself, such a soporific for years since the National League has won the last nine straight and 17 of the past 18, holds out promise. On paper, the starting lineups have scads of future Hall of Famers and no ballot box-stuffing frauds. Each squad leads off with a 15-time All-Star: Rod Carew for the American League and first baseman Pete Rose, who will become the first man ever to start at five different positions in All-Star Games, for the National League.

For once, both teams have natural lineups with speed at the top and no embarrassingly out-of-position players. Only the American League outfield of Reggie Jackson in right, Singleton in left and part-time Yankee center fielder Dave Winfield between them has the built-in possibility of humor.

As a curiosity, Green says that he plans to use his nine pitchers one per inning. What about extra innings? "That's why we brought along a manager who can pitch," said Green, once a Washington Senator hurler of truly Nat-like abilities.

Seriously, Dallas, you aren't really going to use your ninth and last pitcher in the ninth inning of a close game, are you?

"Of course not," said Green. "Just let me worry about that. We won't run out of pitchers."

This will be an All-Star Game with two commissioners in attendance -- A. B. (Happy) Chandler and Bowie (Unhappy) Kuhn. It will also be a game with hope -- Bob Hope, who grew up in Cleveland. Vice President George Bush, the former Yale baseball captain and a bona fide fan, will throw out the first ball before a crowd expected to exceed 75,000 and certain to shatter the old All-Star Game record of 69,831 set here in 1935.

This game has the usual touching sidelights. Mike Schmidt volunteered the comment today that, "The people I've felt sorry for are the shutins and the elderly who depend on baseball so much. My grandmother, who died last year, lived for the games on radio and TV. I think of the people like her."

Frey, asked if he wouldn't rather be back in Kansas City supervising the workout of his rusty Royals, said, with genuine surprise, "I donht mind tellin' you this is a pretty big kick to me. I'm a guy who played 14 years in the minors and never made the majors . . . Plenty of times I didn't even know what i'd be doing for a living, much less managing a major league All-Start team."

Britt Burns, 22-year-old White Sox pitcher, has spent the last three weeks with his father, who si in a coma in an Alabama hospital since being hit by a car. Burns said, "Dad, I made the All-Star team." Upon hearing that, Burns' father opened his eyes in acknowledgment.

Nevertheless, when the All-Star Game of 1981 is recalled, it probably won't be for any of the usual reasons.

This, after all, is the year when the players will watch the fans