Bruce Zabriski was the happiest man on the soggy grounds at Medinah today after shooting a 2-under-par 70 that left him only four shots off the lead in the opening round of the PGA Championship.

A former assistant pro at Winged Foot who is known as Donald Trump's teacher and head pro at the course Trump is building in West Palm Beach, Fla., Zabriski is one of 25 club professionals in the field, based on their performance in the national club pro championship (where he finished 23rd).

Zabriski has played in four PGAs, but missed the cut each time. He was in the first group off this morning in a pairing with his friend, Wayne DeFrancesco, a teaching pro at Woodholme Country Club in Pikesville, Md., who lives in Columbia. DeFrancesco will teach on Zabriski's Florida staff in the winter, and shot 78 today.

"For me, I've got to keep everything in perspective," said Zabriski, 42. "I had the round of a lifetime. To be here is such an honor and then to play like that, better than I really know how to, is a great honor." Zabriski said he was inspired by playing a practice round with Greg Norman, who simply walked up and asked if he could join Zabriski and fellow club pro Mike Gilmore on Tuesday. He also went into Wednesday's news conference with Ryder Cup captain Ben Crenshaw.

"It just jacked me up," he said. "I went out of a whim. I could have walked through brick walls after that speech he gave about the Ryder Cup."

Can he win the PGA Championship, something no club pro has done in the modern era?

"I've never won on tour," said Zabriski, who played the PGA Tour in 1988, '92 and '93, with a best finish of 11th. "I've won on the Nike Tour, but to think you're going to win a major, that would be a pipe dream. For me, finishing in the top 10 or top 15 or 20 would be a real dream."

Last-Minute Changes

Two alternates in the field got into the championship at the last minute, though Bob Friend and Jerry Kelly probably would have preferred to have made it to the first tee under different circumstances.

Steve Elkington, the '95 PGA champion at Riviera in Los Angeles, withdrew from his 12:40 p.m. tee time when his longtime caddie, "Gypsy" Joe Grillo, was taken by ambulance to a hospital after complaining of chest pains and shortness of breath in the caddie area this morning.

Several of Grillo's fellow caddies urged him to see paramedics, and he was admitted to the hospital at about 11:30 a.m. Elkington went to the hospital and stayed until early afternoon. Late in the day, Grillo was reported to be in stable condition and resting comfortably, with no details released by the hospital on what caused his problems.

Frankie Minoza of the Philippines withdrew early today because of a sprained knee suffered this week.

Minoza was replaced by Kelly, a PGA Tour pro from Hobe Sound, Fla., who made the most of his opportunity, shooting 3-under 69. Friend, who has missed the cut in seven of his last 12 tour events, posted a 71. . . .

Frenchman Jean Van de Velde, who blew a three-shot lead on the final hole of the British Open, had a 74 today.