Cowboys Riding Sky High : NFC: They shut down Cunningham, who is benched, turn Smith loose and win, 20-10.

Against the formerly spectacular Philadelphia Eagle defense, the Dallas Cowboys emerged Sunday as the best balanced and possibly best team in pro football.

The Cowboys ran away from the injured and dispirited Eagles during the second half, striking one solid blow after another with running back Emmitt Smith, defensive end Charles Haley and a cast of dozens to win it easing up, 20-10.

So doing, they got even with the only players who have beaten them this season. In Philadelphia last month, the Eagles had overpowered the Cowboys with defense and quarterback Randall Cunningham’s big plays, 31-7.

This time, Eagle Coach Rich Kotite benched Cunningham at the start of the second half, emulating a controversial move by his predecessor, Buddy Ryan, three years ago.

“I didn’t like it much, but I’m not going to start a controversy,” Cunningham said after his backup, Jim McMahon, had made it interesting for a while.

In a brief, lively interlude, McMahon, the former Chicago Bear, drove the Eagles 80 yards to the first touchdown of the game, a two-yard run by Herschel Walker. But they were seldom heard from again.

“We adjusted to McMahon after his first series,” Dallas Coach Jimmy Johnson said.

With the youngest players in the league, Johnson is building a powerhouse here, and they proved it with 10 well-earned points during the fourth quarter to break a 10-10 third-quarter tie after struggling to a 3-0 halftime lead.

Smith, who had his first 100-yard game ever against Philadelphia--163 yards in 30 carries--also had the big play, a 51-yard run setting up Dallas’ go-ahead field goal.

The team with the fewest injuries usually leads the NFL’s strongest division, the NFC East, and so far this season that has been the Cowboys (7-1), who have taken a two-game lead over the battered Eagles and Washington Redskins, both 5-3.

And so after starting the season 4-0 with their high-scoring ballgame against Dallas, the Eagles have lost three of their last four.

Clearly, Kotite blames Cunningham.

“I thought it was time to give him a break and try to get something clicking with (McMahon),” the Philadelphia coach said.

Such a change often shakes the confidence of the benched player, and then the confidence of his teammates, destroying the ballclub for the balance of the season if not longer.

That is what Kotite faces now-- as Philadelphia’s last coach, Ryan, faced it not long ago. The decision to replace Cunningham in a playoff game was later cited by ownership as one reason to replace Ryan.

In Texas Stadium, although Kotite’s offense was mostly standing still during a punchless first half, the Eagles were only three points behind.

“The point is that we made only one first down in the first half,” Kotite replied.

The second half was different.

The Cowboys took over after halftime with their one-name defense and their nickel-and-dime offense. The nickel is quarterback Troy Aikman, the dime is running back Smith, and the defensive name is Haley, the onetime San Francisco 49er who is out to make the world forget the Miami Dolphins’ no-name defense of 1972, Miami’s 17-0 season.

Haley led the Cowboy charge that harried Cunningham out of the game and, ultimately, stopped McMahon--although the charge might not have been enough if the Eagles still had all their old weapons. Since last year, they have lost some of their best players, the late Jerome Brown, Andre Waters, Keith Jackson and others.

And now a quarterback, maybe, although Kotite said Cunningham will start next week.

If the Cowboys are a team with only one name player on defense, the same isn’t true of their offense.

Aikman, for example, is a superb short passer who nickels defensive teams to distraction. During this game, he completed enough passes, mostly short ones, to drive the Cowboys 80 and 78 yards to their two touchdowns.

The scoring plays were both vintage Aikman. They’re in the book as 22- and 14-yard pass plays. But the first was a five-yard throw to backup wide receiver Kelvin Martin, who gave it a 15-yard ride. And the second began as a one-yard throw to fullback Daryl Johnston, who bulled his way 13 yards.

Smith, who is always among the leaders in NFL rushing is a classic NFL running back in the tradition of the great ones, though he weighs only 209 pounds. And during the third quarter he was the star of the turning- point sequence.

The sequence began when a badly-timed Aikman pass was intercepted at the Dallas 22 by linebacker Byron Evans, leading to what would probably have been an Eagle touchdown if the NFL still had instant-replay officiating.

In any case, when Walker was tackled on that play, the ball was across the goal line.

On the field, the officials ruled Walker down on the one-yard line, and in the next three plays the best the Eagles could do--with that kind of field position--was kick the tying field goal, 10-10.

On the next scrimmage play, Smith stole away on his 51-yard run--through the largest hole he has ever had in a Philadelphia game--as the Eagle defense, doubtless discouraged by the impotence of the Eagle offense, lost its grip.

As Smith raced by, the left-side linebacker, Seth Joyner, who usually smashes Smith at the line of scrimmage on that play, was nowhere to be found.

In a wink, the Cowboys regained the lead, 13-10. And on their next possession, they moved 78 yards in eight plays--seven runs and the scoring pass.

“Beating these guys was quite an accomplishment,” Jimmy Johnson said.

The NFC East is his oyster now.

* TOUGH DAY: Flu sidelines 49ers’ Steve Young; Oilers’ Warren Moon suffers concussion. Stories C4, C9.