The chant coined by pro football fans seemed to be the word on the lips of all the contending golfers as they finished the first round of the 78th U.S. Open yesterday. So it was not too surprising that Hale Irwin, a veteran quite familiar with this territory and a specialist at playing the defensive game, emerged as the leader with only a few challengers left on the course.

Irwin recorded a two-under-par 69 to go one stroke ahead of Andy North, J.C. Snead and an 18-year-old amateur, Bob Clampett, the only other players in the field of 153 to better par by late in the day.

Gary Player, Al Geiberger, Dave Stockton, Bobby Wadkins, Phil Hancock and Bille Brask were in at even par. Andy Bean topped a quarter at 72, Jerry Pate led four players bracketed at 73 and 17 others pitched in with 74, a figure most competitors thought par should be.

Jack Nicklaus and Lee Trevino were late starters. Nicklaus struggled to a 73. Trevino was one over through 16.

Causing a late stir in the 94-degree weather was Arne Dokka, a relative unknown from Pacoima, Calif. Dokka, 146th to tee off, was one under with seven holes to play but quickly took two bogeys.

For Irwin, it was a happy homecoming. The 33-year-old graduate of the University of Colorado twice was an All-Big Eight Conference defensive back in football. He also won an NCAA golf title. But his most memorable sucess came in 1974, in the U.S. Open at Winged Foot near New York City.

That course is remembered as one of the toughest in Open history. Irwin prevailing with 287. Cherry Hills is not quite as tough, but nobody was able to put a red three on the leader boards at any stage of yesterday's action and several of the frontrunners found themselves stumbling through the closing holes.

"I played away from the temptation to go for the flag all day and it paid off," Irwin explained. "There is no tomorrow any day here. You can't afford foolish mistakes on this rough a course. Today, I avoided them."

Equally important, Irwin strung together three long putts in a row, midway of the front nine, to build the score that gave him the day's lead. His lone bogey came on the first hole after an eight-iron caught the light rough.

"I over hit the fifth (par-five) on two with a drive and a three-wood." Irwin reconstructed. "I wound up needing a 25-foot putt to save a par. Then I sank a 25-footer on the sixth for a birdie and a 30-footer on the seventh. After that, the round was rather outline."

Except, perhaps, for the par-five 17th, Irwin drove 300 years in the light Mile High air and was faced with a decision of going for the island green in two or playing safe.

"It would have been a foolish gamble at that point," Irwin said later. "Johnny Miller went for it, but he was six over. I decided to lay up, with a wedge. The ball hit about a foot over the moat and ran 30 feet past the pin. But it was the right decision."

North, Gary Player and Mark Hayes, to name but three, were not so fortunate nearing the finish. North was two under and tied for the lead coming up 38 after a fine one-iron shot off the tee. He pushed a two-iron into the bleachers, had to take a drop and scramble for a bogey.

Player, the Masters champion looking for a possible Grand Slam, should have been at least one under but settled for par.

"I played the last hole like a chicken," the South African declared. "I actually played my drive into the rough on the right, then hit a six-sood out. That's right. A six-wood. Trevino tipped me about it. I think it's more effective, in tough rough like they have here, than an eight-iron."

"I just played a lousy shot off the tee." Player repeated. "No guts. But I love this course. It's a pleasure to play. The premium is hitting the ball straight, andt the altitude is similar to what I play in at home, Johannesburg, which is 6,000 feet."

Player was one of the few leaders to go to a driver often yesterday.Seven times to be exact. The bigger hitters struck only four or five drivers into this tight fairways embroidered by brutual rough.

Young Clampett was one of the few players to beat the backside, going two under. He required only 28 putts for the round and several of those were from downtown Denver.

"I consider myself a good putter, but not exceptional," the fresheman at Brigham Young University remarked. At 18, Clampett is the youngest competitor in this Open. He was six weeks old when Arnold Palmer won the 1970 Open here.

Jesse Carlyle Snead, a nephew of the legendary Sam, supplied one of the day's steadiest rounds, 35-35. A bogey-six on the fifth hole represented his only mistake.

The day's hard Luck Trophy went to Hayes. 1977 Tournament of Champions winner. The 28-year-old Oklahoman was two under, sharing the lead with Irwin and North, and in perfect position for a birdie try at No. 17. He went for the green, saw his ball trickle into the moat in front of the island, instead, took a bogey six - then became so upset he caught a most unlucky triple-bogey seven on the 18th, two-putting from four feet.

Dave Stockton was another to fall back on the 18th taking a bogey after-driving into the right rough and coming out short of the slightly elevate green with a four-wood.

"I still like my chances," the veteran volunteered. "The big hitters don't have that much of an advantage. The rough is a great equalizer, if you're not careful. It's a typical Open."

The distinction of striking the day's best shot went to young Bobby Wadkins of Richmond, Va., who wound up at 71. Wadkins hit a five iron on the par-three, 208-yard 15th hole and "never saw it go in . . . but I knew it was going to be close. When I saw the guys behind the green jumping up and down, I knew that it was one. They said the ball hit about six inches up on the flagstick and dropped in the hole."

Hubert Green, the defending champion, found it difficult to talk about on exceptional shot, at 76. "I drove into the rough five times," he said.

Palmer fell apart on the closing holes, three putting from eight feet on the 16th and gambling poorly, into the water on 17. Tom Watson, out in 40, settled down for 34 on the back nine to stay in contention, four strokes behind Irwin.