Hale Irwin had not been heard from lately, until he posted a 66 yesterday in the Kemper Open. After a first-round 74, he even had made tentative plans to scout Baltusrol today, site of his U.S. Open defense in two weeks, if he missed the cut here.

It has been almost a year since Irwin suffered a monumental letdown when he did not add the British Open title to his second U.S. Open crown. When he is on, Irwin plays a game ideally suited to Congressional Country Club.

He is a flawless long-iron player, a requisite for Congressional's 7,054 yards. He is tenacious, a fighter who can persevere against the treachery Congressional offers. He is phenomenal around the greens, which is a must with these putting surfaces. He is a strategist, and conservation pays dividends here.

Irwin's game started to come around two weeks ago. Yesterday's four-under-par effort -- the best round of the tournament thus far, leaving him three shots behind leader J.C. Snead -- was its fruition. He had 10 birdie putts of 10 feet or less; he made four.

"I've been working very hard on my game the last month," said Irwin, who at 34 ranks seventh in earnings on the PGA's all-time list. "I'm trying to salvage something for the year. Maybe that hard work is surfacing."

He has won $48,000 this year and ranks 41st in earnings. He missed the cut in four of his 13 previous tournaments, including the Masters. His ninth-place finish at Fort Worth two weeks ago was only his second top-10 finish of the year.

What was wrong with his game?

"Everything," Irwin replied.

He still was cautious yesterday, partly because it is his nature and partly because he still is not satisfied with his drives. He is well aware that an errant driver here produces enormous headaches.

Although he missed six short birdie putts yesterday, and many more Thursday, he was not espcially disappointed with his putting as he chased Tommy Jacobs course record of 64.

The key to his putting yesterday was striking the ball well.

"Early in the year, I wasn't putting well," Irwin said. "Yesterday, I hit a lot of putts the way I wanted to, but I wasn't reading them well."

It wasn't a fantastic putting round. I can't say that. I had so many close putts, sometimes the hole got in the way."

Then he was the serious craftsman.

"The greens here are unpredictable, but not bad. The greens are traffic prone. That will be better tomorrow because half the field will be down the road."

Irwin has been down that road frequently in the last 11 months, piling up most of his $154,000 earnings in 1979 in the first half of the year, prior to the British Open.

"In retrospect," Irwin said, "I put a lot into the U.S. Open and got a lot out of it. Leading the British Open and not winning it took a lot out of me."

He said the British press continually played up his possiblity of becoming a rare winner of the two Opens in the same year. Only Lee Revino, in 1971, has done it in the last 26 years.

"The situation over there was built up to the Second Coming," Irwin said. "Even I got excited."

Then came the letdown, which he called "a natural."

But, he added, "It was a lot deeper than I thought it should be. But the history of my game is to let my game down and work it back up. That's best for me."

He seems to be reaching his form.But he is still cautious, respectful of Congressional and unwilling to look ahead to his prospects in the Open on a course he has never played.

"I really don't want to put the cart before the horse," he said. "There are still two more rounds to play here. This is not your average small tournament. There's a lot of money on the line on a prestigious course."

Then, he added: "Tomorrow, I may go out and fall off the end of the first tee."