The pennant contender's best friend arrived here tonight -- the Chicago Cubs.

Like a platoon of cavalry coming to the rescue, the Cubbie Bears got to Three Rivers Stadium just in time to hand a game to the Pittsburgh Pirates when the Bucs needed it most.

The Pirates' 6-1 win over the inert Chicagoans, coupled with Montreal's 3-2 loss to Philadelphia, reduced the Bucs' magic number to two and raised their league lead to two games.

The National League East's I'll-be-home-for-Christmas pennant race, which just hours ago looked like it might require a computer to unravel, now may be on the brink of completion.

The good news arrived all at once tonight at 10:50 p.m.

The Bucs, after weathering 117 minutes of rain delays, got the final Cub out of the fifth inning at that moment, making their 5-0 lead official and immune to future moisture.

Much later, after midnight in fact, the Pirates' hulking 250-pound right-hander, Jim Bibby, would finish his four-hitter with 11 strikeouts. No one there doubted, however, that the Bucs' most dangerous enemy was the steady drizzle, not the unsteady Cubs.

No sooner had the Pirates survived that threat of a washed-out lead, than the vast center-field scoreboard told the 14,778 fans the only thing they wanted to know: The Phillies Win!!

"I never thought the Phillies would win a game that would help us this year," crowed Buc Manager Tanner, who, if he was not ready to proclaim the Expos dead, was willing to put some salt on Philadelphia's year-long wounds.

Though the cheering may have been a bit weary in this soggy, drawn-out affair, the Bucs, nevertheless played crisply, building that 5-0 lead after two innings and supporting the 6-foot-5 Bibby with brilliant defense, including five leaping or diving stops by infielders.

Bibby and his saviors -- Phil Garner and Bill Madlock -- were a mutual admiration society in the jumping Pirate clubhouse.

"There ain't a human being alive who could hit the stuff you had tonight," said Garner to Bibby. "You were awsome, my man."

"I'm not going to shake your hand," said catcher Ed Ott to Bibby, protecting his right hand behind his back. "You almost knocked off my left hand with that fast ball of yours. Now you want to squeeze off the other one."

That bravado was merited. Anyone who was here tonight, however, knows the other half of the truth. The Pirates had help -- wagonloads of the kind that a tired team needs in September.

These fifth-place Cubs, who have played fierce .324 ball against the Pirates and Expos this year, were the equivalent of a CARE package to the drained Bucs who were pasted for 17 hits by St. Louis Thursday afternoon.

The Bruins can hit some and they can pitch some. But they can't field at all. Once the ball is hit to them, they become a team for the ages -- the Middle Ages.

It is not their 154 astronomical errors that distinguish the Cubs, but the panache with which they blunder. Who says it is easy to field on artificial turf? The Cubs could look mystified on a pool table.

Over the years, Cub starter Rick Beuschel has suffered much -- more than 100 unearned runs, 19 of them this year in his 18-win season that easily should have been 20 or more.

"We do not play sound fundamental baseball," said Reuschel. "It should be the easiest thing in the world. But we can't do it.

"There are ways to make anybody play good fundamental baseball," said the 250-pound Reuschel, warming to the topic. "Fine 'em. Yank 'em out of the lineup. Embarrass 'em."

Or kill 'em?

The pitcher's mound tonight was in danger of becoming the pitcher's depression with the starting tonnage amounting to 500 pounds. But, while the Bucs took weight off Bibby, the Cubs added concrete blocks to Reuschel's burden.

His first pitch was lined at shortstop Ivan DeJesus -- a judicious choice since DeJesus has 28 errors. Why not the best?

The ball struck squarely in his glove, then ricocheted into left field as though it had struck a skillet for a "hit."

On Reuschel's second pitch, the Buc runner stole, arriving well ahead of the graceful one-hop throw of Tim Blackwell.

Perhaps annoyed, Reuschel threw a brushback pitch. But hitter Tim Foli, as he fell, accidentally laid down a perfect sacrifice bunt. Foli was out by 91 feet. Omar Moreno stood on third. Reuschel looked as though he did not wish to proceed.

Nothing happened on Reuschel's fourth pitch. It was his highlight of the night. Dave Parker splashed his fifth toss to right for an RBI hit. Moreno had completed his Around-the-Bases in-Three Minutes trip.

Before the inning was over, John Milner lined a hit-and-run shot to right field that should have been an easy double play with Parker trapped off first by 100 feet. However, in Chicago, there's a riddle: "What has two i's, two t's and no hands? Answer: Larry Biittner."

Let us be brief. The ball struck right fielder Biittner several vicious blows, fell to the turf exhausted and eventually was returned to the infield with Pirates at the corners. Reuschel escaped the inning, but he returned in the second inning a nervous man.

Reuschel walked two Pirates as though beset by a premonition. Then it happened, the play that made this night worth the hours of rain and fog.

Tim Foli grounded a single to left. Dave Kingman charged the dribbling ball, intending to scoop it and fling it homeward. How an almost motionless ball can elude a 6-foot-6 man nicknamed King Kong has not been determined. But Kingman never touched it.

By the time the magic sphere, now at a halt, was apprehended, two runs had scored and various Pirates had advanced a total of seven bases.

And this game was over. Reuschel was dazed. Parker hit his next pitch a great distance over the right-field fence, almost striking the 10-foot-high sign of a Cobra with the No. 39.

The Cub defense did not play with the same verve after Reuschel left for a pinch hitter in the fifth. Oh, DeJesus was almost beheaded by a grounder in the sixth, and the recipient of the "hit" eventually scored with the aid of a wild pitch.

It did not matter. The visitors had needed only two innings to leave their calling cards. Thereafter, what they played was dull stuff and resembled baseball.