When an NFL coach enters the Land of Legends, odd powers come to him. Vince Lombardi was said to be able to stop rain on command. Today Tom Landry was pacing the sideline with 40 seconds left and the Falcons trying to muster one more miracle.

"Come on," Landry yelled to the Dallas Cowboy defence. "One interception."

Well, Atlanta quarterback Steve Bartkowski had his arm cocked when the final word left Landy's lips. No sooner had it become a puff on this nippy day than the ball landed in the chest of Cowboy Cliff Harris.

Nicely done, Tom.

As always, Landry's mind, if not his will, was significant. But not as much as Danny White's arm and his legs-and the defence in the second half. In this playoff test, the Cowboys overcame as many problems as most teams get in five games.

In the first half, the Cowboys lost four fumbles and their quarterback, Roger Staubach, who resembled a newborn colt as he tried to gain his feet after a wicked, late hit.

On the second try, Staubach was able to walk. But the concussion kept him out of the final 30 1/2 minutes, so White was able to realize one of his dreams. He drove the team to victory, as the offense knew he could.

"Nobody has any reservations when Danny gets in there," said left offensive tackle Pat Donovan. "Even if it looks like he's going to lead us to . . ." He paused, a Stanford man keeping his dignity.

"Honesty, we have so much confidence," he said, getting positive again. "He does just as well as Roger there is no letup with him in there. Now Roger might not like that, but I think it's true.

"He's thinking all the time. There's no screwup factor." Well, there was at least one, in that six-inch drive Scott Laidlow executed for the winning touchdown midway through the fourth quarter.

Either Drey Pearson brought in the wrong play or White lost it in translation.Whatever, White changed what was supposed to be a pass play into an inside handoff-and the Falcons blitzed themselves into position of r Laidlaw to score.

White has been priming himself for a situation such as this for three years, but with the nagging feeling that his lot in life was to be the perennial backup. Falcon linebacker Robert Pennywell gave him his chance, with a hit that drew a 15-yard penalty and the wrath of Landry after the game.

"There's no place in football for the kind of shot he (Staubach) got," Landry said. "It should be dealt with by the commissioner (Pete Rozelle, who attended the game).

"You don't hit a guy with an elbow on the side of the head unless you meant to do it. All I know is Roger was hit by a forearm to the head." (After the game, doctors said Staubach's head was "clearing" and that he would be able to practice).

Though he said he was as fluttery as an armchair quarterback would be in similar circumstances, White seemed poised-especially on a first-and-goal play that seemed destined to yield a loss but in fact produced the tying touchdown midway through the third quarter.

The play was a rollout right after an inside fake to Laidlaw and the intended receiver, tight end Jackie Smith, was covered. Instead of lowering his head and darting toward the end zone, White remained at cruising speed, with a Falcon closing in.

"Run," yelled Cowboy president Tex Schramm in the press box.

White had a better idea.

While he was keeping his feet-and his wits-Smith was maneuvering into the only open space available in the end zone, about a two-yard square area. And White suddenly hesitated and flipped him the touchdown pass.

Earlier, in his regular role as punter, White saw the Falcons drop into a return formation, faked a punt and ran 12 yards for the first down that eventually led to the first Dallas touchdown.

On and off the field, White appears cut from the Staubach mold.

"He's been trained by No. 12," said defensive tackle Larry Cole, himself a free spirit. "He's flawless."

And confident. During training camp this season, a bank was using him for a commercial with the theme momentum. Before the taping, he was given a script that began: "Hi, I'm Danny White, backup quarterback for the Cowboys . . ."

White read that, stopped and said to the director, apparently with a straight face "By the time training camp ends (and the commercial would be shown), I'll be the starter." The director convinced White there would be another commercial shot when that came to pass.

When the game ended today, White was one of the final players to leave the field, savoring his moment of triumph and saluting his public with a hearty jab at the air with his fist.

"That's the hardest hitting team I've ever faced," said White, smiling. "Which means they hit harder than the Jets last week." That was a rare White start-and everyone, White included, hopes it will be the last for some time.

White does not want to win the position because of an injury to Staubach. Of his future, he said: "If I could be Roger Staubach in 10 years, that would be my dream. He has known all the success you could want, done everything that can be done. Yet he's kept his ideals, not let his head get loose.".tUnless a Robert Pennywell has an elbow in it. CAPTION: Picture 1, Steeler John Stallworth makes difficult touchdown catch in fourth quarter, one of 10 completions for a playoff record. UPI; Picture 2, Denver's Bill Thompson flings Steeler receiver Lynn Swann to turf, but officials allowed fourth-quarter score. AP; Picture 3, Franco Harris of the Steelers is chased by Louis Wright of the Broncos. Harris scored his second touchdown of game. UPI