The booing has started here. It is soft, more resigned than venomous.

On Thursday night the Chicago White Sox left town and they heard smatherings of it. On Friday afternoon the Chicago Cubs returned home and the sad sound was waiting for them, too.

Chicagoans have a hard time believing that their fantasy of a World Series on the "L" between White Sox Park and Wrigley Field has gone up in smoke so quickly.

No, no, that's not right. They find it all too easy to believe, almost inevitable. They knew this double collapse would come, knew it as surely as they sensed something was wrong when two Chicago baseball teams were each in first place for the entire month of July.

But did both the Chisox and the Cubs have to collide with reality in the same week?

Couldn't just one of them have held on past the dog days into the stretch?

And on this bleak Friday just past did both teams have to lose such symbolic games within hours of each other?

First, the Cubs hosted the defending East Division champion Phillies to start a four-game series. It was a last chance to circle the wagons, to whittle a three-game deficit and keep the dreaming alive. Everybody - sick or well - plays in this one, right? No malingering, boys, okay?

Wrong. The Cub's leading hitter, Jerry Morales (.322) reported an unusual injury - Astro Turf knee. Seems playing on the evil stuff in Pittsburgh had made Morales' shin too sore to play, especially against super lefthander Steve Carlton.

Shortstop Ivan DeJesus, the man Cub manager Herman Franks calls"the key to the team," said he thought his sore right forearm should get a day's rest.

Since the Cubs had just had an off City on Thursday. Franks barely tried to hide his disgust that stars would ask for a breather when half the Cub team is ready for intensive care.

"What am I supposed to do, huh?" said Franks, a gruff gentleman who speaks his mind. "If a guy tells me he can't play, he can't play. Who am I to doubt him? I got to play whoever's left."

The "Whoevers" got crashed, 10-3, on six Phillie home runs. Franks rushed ace Rick Reuschel, still nursing a back injury, into the first-game fray to compensate for the anemic lineup. Reuschel, who desperately needs rest, gave up seven earned runs for the second straight start.

As though to embarrass his mates, Cub first baseman Bill Buckner - who has a newly sprained hand, two pulled leg muscles (one per thigh) and a chronic ankle injury - insisted on playing. After crashing a ball off the center field vines, he arrived at second base running like a potato-sack racer pushing a wheelbarrow.

If the Cubs, losers of 10 of their last 14 have simply run out of talent and stamina in a brutal division, the White Sox seem finally to have been unhinged by their own atrocious fielding and baserunning fundamentals.

Just hours after the Cubs had plummeted to third place on Friday, the Chisox - first-place tenants since July 1 in the AL West - saw their lease expire and were evicted into second place.

If one man's voice ever expressed the angst and frustration of an entire city, it was White Sox announcer Harry Caray, who sounded as if he was going to commit his name, when he telecast the Chisox' ludicrous 10-7 defeat from Texas.

"Did Alan Bannister ever have a weak cut at that . . . and the Sox waste a leadoff double becuase nobody advanced the runner . . . I'm not sure but that ball seemed to bounce between Ralph Garr's legs . . . we gotta be the toughest team in history to issue a walk to. We'll swing at anything . . . we gotta get 11 runs now to win this game. Friends you just can't win without pitching," went Caray's accurate and exasperated commentary.

As Ranger reliever Darold Knowles put it "It's catching up to them, finally. No matter how well you hit the ball you gotta get hurt in the long run if you can't catch it or throw it. I'm surprised they were up there this long."

For Chicago, that is the pity of this sudden double indemnity. "All this has been just a dress rehearsal for the pennant race," said Texas manager Billy Hunter. "The real thing doesn't begin for a couple of weeks." After more than 100 games of anticipation, it now seems that the two Chicago entries may not be around for opening night.

"Yup, they're goin' down the drain together," said 75-year-old taxi driver Albert Gyse, gesturing with a right hand sculpted by decades of foul tips in his years as a catcher with the Homestead Grays and New York Black Yankees of the Negro Leagues.

"It's a rotten shame. This has been a beautiful summer. People goin' out to the ballparks again. Business has been good," Gyse winked, then turned serious, then annoyed. "Just plain bad management," he snapped. "I could manage either of those teams to the pennant," and he was off discussing the sins of a dozen different home run-hungry Chicago players who won't play "team ball, real baseball."

Even the players sympathize with their suffering supporters. After that first ominous, wave of boos on Thursday, Garr defended the Sox's fans, saying, "I still think they're great, I can understand they're disappointed right now. So are we."

The Cubs' home-run leader, Bobby Murcer, greeted with hoots after three strikeouts Friday, gave a sarcastic tip of the helmet to the fans. But latter he relented and insisted, "Boos? I didn't hear any!"

Certainly, neither club deserves a boo. The Cubs in particular have player over their heads for months. Ex-Cub Ernie Banks attributes their inspired performance, and by inference their collapse, to one player - Bruce Sutter, the "Ubermench" of relief pitchers who is now disabled.

"He was the most humiliating relief pitcher I ever saw," said Banks of Sutter, whose statistics - just 50 hits, 12 unintentional walks and 102 strikeouts in 84 innings - still seem impossible. "Guys were missing his split-finger fast ball by six inches to a foot. You can't laugh that off.

"Pete Rose, Johnny Bench, Lou Brock all told me he was the closest thing to an unhittable pitcher they ever saw. A great relief pitcher is a wonderful equalizer for a team that isn't certain of its ability. He made the quality batting orders look foolish."

Now Sutter, due back off the disabled list on Aug. 23, is an enormous question mark because of an only vaguely diagnosed lump in his shoulder that seems to be aggravated by just one thing - pitching a baseball. No wonder Banks inadvertently speaks of him in the past tense.

If the Cubs - their pitching in batters, 11 players currently injured, and their never-powerful lineup now infiltrated by the likes of little Mick Kelleher - seem finished, the White Sox still have hope.

The Chisox don't "come to bat," they attack. Their impatient mesomorphs reverse the customary balance of initiative between the mound and home plate. Instead of the pitcher dictating the action, the White Sox upset normal theory by swinging at all reachable pitches and driving them to all fields. How can a pitcher cultivate his atmosphere of legerdemain in such a madhouse?

Nevertheless, even if the White Sox continue to lead the known universe in offense, their spotting pitching, especially in the bullpen where Lerrin LaGrow has gone sour, and their Where-am-I defense will probably derail them. Only one regular Sox pitcher has an ERA under 3.96.

"Both teams have burned out their pitchers," said Joe Alfonso, an early-arriving fan at Wrigley Field today. "They couldn't resist staying at the top as long as they could."

Then he paused, a typical middle-aged fan in a city lifelong allegiance to both clubs is common. "But I guess it was worth it," he said. "It's a miracle they both lasted this long. Yeah . . . good while it lasted. The only time a Chicago team rooted forever won a pennant I think I was still driving my old Hudson."