Many things in sports are surprising. Some are even moderately shocking. But occasionally a mutation occurs that is so annoyingly unreasonable that the gears of the sporting mind grind to a halt as though clogged with sand.

To wit, the Chicago Cubs.

Coming on the heels of the rest of this season's wacky happenings, it almost seems a disrespectful joke on the predictable old game for the Cubs to have the best record in baseball.

But there it is. The Los Angeles Dodgers opened the season 30-10 and the world rushed to their blue doorstep to hear the secret. The Cubs have gone 30-10 since May 1 and now have a better record than the Dodgers (37-19 - 661 to 39-21 - 650). Few have noticed.

"The world's finest front-runners are just beginning to show up," gloated Cub outfielder Gene Clines, who is hitting .338, 60 points above his career average.

"Believe me, this team is just waiting for them. We're going to make a lot of people eat their words. I'm gonna ask every one of them, 'Where were you in April when we needed support and encouragement?'"

From top to bottom, the Cubs exude a sly glow. "I hear about the Big Red Machine and all the other nicknames," said manager Herman Franks yesterday, savoring his fourth five-game winning streak and a 4 1/2-game division lead, "but we've ridden right past 'em on our little blue bicycle."

Even the Cub brass, however, recognizes that this team better keep the little blue training wheels on as long as possible.

"I know water seeks its level," said general manager Bob Kennedy, the man who rebuilt this team with trades after taking over last winter. "A lot of people are waiting to see if we're for real.We'll need help from every man on this team to stay where we are.

"Right now, we live one day at a time. All the praise . . . I take it with a grain of salt. When you trade for people who get off to a fast start, it makes you look smart. But I've been dumb before, and I will be again."

The Cub locker room offers a fascinating potpourri, whether this team runs the first pennant in 32 years up the Wrigley Field flagpole or lapses back into last place whence it came.

"The one thing we're pretty proud of," says Kennedy, "is that we've changed the complacent, show-up attitude of the old Cubs. We've now got 25 guys who want to win, not three or four."

That aggressive attitude starts with the laconic Franks, who had the best managing percentage in baseball with San Francisco from 1965 until 1968, then retired to build a small fortune in Salt Lake City real estate.

In public, Franks is still as untalkative as someone who is renowned for investing other people's money. But in the clubhouse he is the "king of needles."

"Herman is the world's champion agitator," said Clines, quickly inserting a barb of his own." Of course, it's taken him two months to learn the basic soul handshake. He was away from the game too long. I have faith that in another two months he'll just about have the three-phase shake, mastered."

Knowing his team cannot win by the book, Franks has gambled relentlessly. Last week, Franks ordered Jose Cardenal to lay down a bases-loaded squeeze bunt in the 11th inning of a 0-0 game.

Cardenal, a .299 hitter in 1976 who has ridden the bench this season, showed none of the showboat tendencies so prevalent in his previous baseball incarnations.

After a perfect bunt, Cardenal explained his new teamplay theory simply: "Jose just go along with the program."

Nearly all the Cubs have gone along with the new program.

Bobby Ray Murcer, acquired at the price of a batting champion, has driven in the runs (37 already) that Bill Madlock could not, Murcer sits in a sawed-off rocking chair in the locker room and plays his "Up-Against-the-Wall-Redneck-Mother" tape deck. "I'm a sophisticated cowboy," said the Oklahoman. "There's no manure on my shoes."

The bonus in the Murcer-Madlock trade was Steve Ontiveror, a "throw-in" how hitting .309 at third base. Next door at shortstop is the Cub's No. 1 Miracle - Ivan Dejesus - the man who was likewise a throw-in in the Bill Buckner-for-Rick Monday deal.

"You have to trade quality players to get quality players," said Kennedy. "But in both trades we not only got quality-for-quality, we also got numbers (two-for-one)."

Buckner, hitting .292 and still sometimes wearing his Dodger jacket in the dugout, has at long last brought the Cubs a good glove at first base. He worries, however, that "I'll be the first No. 3 hitter in history to go a whole season without a home run."

Among these Cubs, a homerless first baseman would not seem out of place. The last Bruin home run came on - believe it or not - June 1. These inhabitants of Wrigley's "friendly confines" have launched just 31 of the new Rawlings rockets.

Fortunately, hitting coach Lou Fonseca has spread the spray-hitting gospel that made him perhaps the least-known career .316 hitter in history. Prize pupil Manny Trillo, a career. 189 hitter, is at least temporarily leading the league in hitting at .367 and symbolizes perfectly the improbability of the whole Cub escapade.

Nevertheless, it is not the place-setting single of the keystone vacuum cleaners, Trillo and DeJesus, nor the clutch hitting of underrated centerfielder Jerry Morales (.468 with men on base last year) that will keep the Cubs afloat.

It is a kid relief pitcher named Bruce Sutter who is the Cub life raft. The pitching staff is built around the 24-year-old fork baller.

These days, Wrigley's Bleacher Bums wear tee-shirts that say, "Bruce Sutter - Oh, what a relief he is." But if the magician with 17 saves, a 0.79 ERA in 31 appearances and an unprecedented ratio of 67 strikeouts to five walks in 57 innings, suddenly turns sour all the Cubs will have actual indigestion.

The tall, pot-belled Cub pitching staff of Bill Bonham, Ray Burris, and Rick and Paul Reuschel (affectionately called Whale I and Whale II) are durable journeymen who have learned how soothing a seventh-inning showed can be when Sutter is on the mound.

For now, all the Cubs feel that way Victory is their new toy: defeat and lost confidence just a rumor.

"I'll never gorget the day we moved into first place," said Cines yesterday. "We'd beaten the Pirated three straight two weeks ago and the appeal wouldn't leave their seats until the flags above the center field will were changed to show that we were on top and Pittsburgh was second.

"When the Cub flay was put on top, there was one big gigantic roar. Those are my type of people."

And so, one day at a time, the Chicago Cubs - the team that has the best around in baseball, the team that has not hit a home run in two weeks - keeps its flag of paradox aloft.