Two improbable conditions perplex a lifelong baseball man almost equally: those times when all four tires go flat at once, and those even rarer occasions when the entire world is perfect.

"Everybody is doing everything right," said Boston manager Don Zimmer, his eyes squinting suspiciously, like a man who senses a practical joke and is determined not to get caught.

"I told (reliever) Bill Campbell to take the day off on Sunday and take his wife to the beach," said Zimmer. "But he wouldn't go. He kept saying, 'If you need me for an inning, Skip, I'm ready."

Zimmer has watched so many pieces of so many Bosox puzzles fall into place at just the right time that he is getting antsy. The little manager with the metal plate in San Diego and he knows winning a pennant can't be this easy.

His team has hardly needed him for the last 13 magic days. Before tonight's game with the Baltimore Orioles, Zimmer's gang had won 10 of 11, 13 of 15, and led the American League East by 3 1/2 games.

Last weekend, the Red Sox hosted New york in Fenway Park. They merely hit more home runs - 16 -in three games than any team in major league history.

Nevertheless, after Saturday's second game, Zimmer admitted he had a tiny problem. Campbell, the solid-gold bullpen ace, was tired after saving 14 games, winning five and building a 1.15 ERA in 23 appearances since April 26."It'd be nice if I could rest him a coupla days," said Zimmer, knowing his patchwork staff had only 14 complete games to its name.

So on Sunday, aging Fergie Jenkins faced only 29 men in his three-hitter. Monday, Mr. Rick Wise, ERA 6.68, pitched to just 31 in his two-hitter. "Will that suffice, Mr. Zimmer?" asked the baseball gods.

Actually, Zimmer has not stopped saying, "Thank you," to the game's unseen powers since opening day. Every favor the Red Sox have asked has been granted.

Boston made three offseason moves and each has been a bonanza. Campbell, the $1.2 million free agent who was Fireman of the Year last season, has helped most.

The swaggering 6-foot-3 righthander who has almost every pitch and motion in the book, expected to be adored in Boston since he was just what a team with a shaky, aging pitching rotation needed.

But he did not understand that the Hub likes its baseball pure. "When we tried to buy Joe Rudi and Rollie Fingers last summer," explained one Boston writer, "people here actually were against it. Buying a pennant is something New Yorkers would try to do. It's not Boston's way.

On opening day, a huge sign above Campbell in the bullpen said, "Sell Campbell. Bring back $1.50 bleachers."

When the screwball-sinker artist started atrociously, losing his first three games. Boston shuddered. "We're getting what we deserved thought the grandstand moralists.

But they were discounting two things. The Yankees started off even worse - 28 - a respite that may have saved Boston's season. Secondly, Campbell seldom starts quickly because his success depends so much on honing several corkscrew motions and blending his deception with control. For weeks it seemed Campbell would fall behind the bat boy 2-0. Now he seems to come to the mound with an automatic 0-2 count on his victim.

If Campbell was a face (and record) saver for the likes of Luis Tiant (5.47 ERA), Bill Lee (4.47) and Wise, the Red Sox batting order has been a Boston pitcher's dream.

With 96 homers in 63 games, including a stunning 71 in their last 35 contests, the Bosox are ahead of the alltime record pace of the 1961 Yankees of Mickey Mantle and Roger Maris, who hit 240 homers.

Even th Red Sox point out that having played 36 games at their Fenway launching pad to only 27 on the road makes the projection questionable. But the club record of 203 is almost sure to fall.

In Fenway, the Boston lineup is terrifying. The addition of George Scott and Bernie Carbo helped make it so. Milwaukee gave up on both a and graded them for Cecil Cooper. Scott, of course, is leading the Nmerican league in home runs with 18 after returning to the town where he broke in.Carbo is hitting .313 with his inside-out batting stroke. He plotted three El Cheapo homers into the screen in two days against New York and laughed all the way around the bases.

"The Boomer loves Boston," says Scott, who always refers to himself in the third person. So does the sensitives Carbo, who needs public affection to play well and will have it forever in Boston after the home run he hit in the sixth game of the '75 Series.

It is typical of the eerie improbability that surrounds these Red Sox that Scott is having his best slugging season while being in the worst shape of any player this side of a Japanese Sumo Slow-Pitch league. A serious case of the fats may be helping Scott's opposite-field power, but it also is helping him move toward the first 40-homer, 40-error season in history. The Boomer, so vain about his navy blue glove, has 15 errors. "The Boomer's missed some strange ones," he says in disbelief.

Zimmer and his staff can take credit for many of the Red Sox' other great batting leaps forward.

Zimmer's No. 1 brainstorm was turning Rick Burleson from a No. 8 giveup hitter into a leafoff man who batted .340 for the last half of 1976 and is at .310 this year. Burleson, Zimmer reasoned, only needed a steady diet of fast-ball strikes to be a relaible hitter. Anyone who bats in front of the Bosox shock troops sees good pitches.

Burleson rivals Fred Lynn and Carlton Fisk as Boston's best "situation hitter." While other Sox play "Screeno" in batting practice, those three call out situations to each other - "man on third, one out" . . . "man on second, none out" - to see who can deliver the sacrifice fly, the grounder to second or th hit-and-run that inside baseball men respect.

No one bat in the Boston order is hotter than might be expected. In fact, Lynn's average will certainly rocket from its current .231 now that his sprained ankle is improved. What makes the Red Sox frightening, even to themselves, is the fact so many hitters are stoking at maximum force.

"I've seen teams get hot," say Carl Yastizemski, hitting .326 and in the midst of one of the great bingers of his Hall of Fame career. (But two or three guys were always struggling. Right now, we've got nine guys fighting to get to the plate and one (Dwight Evans - .296 average, 11 homers) who's coming off a pulled muscle and can't even get back in the lineup until somebody cools off."

Pitchers don't like to think about the Red Sox right now. "I wouldn't pitch to us unless I had a Sherman tank," says Lee. The new Burleson is still a mystery. The new Rawlings ball has made Yastrzemski a home run hittert again. Fisk has drastically closed his stance and jumped from last year's .255 to 342. No one has a book on him yet. Jim Nice, 24, the man they say will hit 400 homers in the 10 years of his prime, once he figures out what the game is baout, is so hot it hurts - .568 (27 for 48) for the last 11 games.

The more feats of power the Bosox perform, the more they think they care acpable of. After watching his team slug an unbelievable .917 for the three games against the Yankees, Yastrzemski deadpanned, "I doubt if it hurt either our morale or our confidence. What's it say to the Yankees?"

It is time for Boston's rivals to grit their teeth. "I don't care if they hit 412 homers in a week. What's the difference," said New York manager Billy Martin in the aftermath of the weekend blitz. "This is June. If they were six games in front, we'd still beat'em.

"Campbell can't go all the time . . . We've got the beach. They're vulnerable to injuries in the infield and behind the plate. And Bill Lee isn't going to win for them. Not because he called ma a Nazi, but because the bearded lady hasn't got anything left. I could make a comeback off him.

"I'm thinking of using Lee to pitch batting practice at the All-Star Game so our hitters can scare the National League," brazened Martin, standing erect on the burning bridge.

The pursuers in New York and Baltimore may be right. Pitching, defense and speed are constants. Hot bats are baseball's most treacherous variable. But on this first day of summer, the hottest item in baseball is the Boston Red Sox.