BRITISH OPEN : No Bad Breaks for Them : Golf: Baker-Finch (64) and O’Meara (67), each going for first major, tied after three rounds.

If his good luck holds out, if his bad back holds up and if he doesn’t break a leg in mid-round--as another contender at the British Open golf tournament did Saturday--maybe Mark O’Meara will capitalize today on everything he has learned about playing golf since he sneaked onto his neighborhood course in Mission Viejo as a kid and played for free.

O’Meara is one of the co-leaders of the 120th British Open, along with Ian Baker-Finch of Australia, whose 64 wiped out the Royal Birkdale course record. They have a one-shot edge over Ireland’s Eamonn Darcy and Australia’s Mike Harwood and a two-shot margin over Seve Ballesteros of Spain going into today’s decisive round.

O’Meara shot 67 and both he and Baker-Finch--who sometimes water-ski together near their adopted hometown of Orlando, Fla.--eagled the 17th hole and birdied the 18th to charge into first place.

“It sends chills up and down your spine when you come up 17 and 18 and hit a good shot here,” O’Meara said.

Neither he nor Baker-Finch has ever won a British Open--nor, for that matter, have any of the top 30 place-holders except Ballesteros, who has won this tournament three times. The leader board here is something out of Golfers Anonymous, with many of the best-known names having faded a bit.

Baker-Finch--also the third-round leader of the 1990 Open, at St. Andrew’s--put together 32s front and back with textbook iron play. His 195-yard five-iron at the 17th landed 20 feet from the flag for his eagle. At the 18th, with his ball buried in a divot, Baker-Finch blasted another five-iron 184 yards, leaving himself a six-foot birdie putt.

His 64 included six birdies and an eagle.

Eager to win a major, Baker-Finch is doubly eager to avoid a repeat of last year’s tournament, when he was so easily overtaken by Nick Faldo that “I might as well have just been a marker at his side.” The Australian also lost a playoff in last week’s New England Classic on the PGA tour and fears a reputation of being unable to handle pressure.

A worse fate awaited Richard Boxall, an undistinguished Englishman who was having the time of his life Saturday, sitting two strokes behind the leaders, when he heard something crack after striking his tee shot at the ninth hole. After crumpling to the ground, Boxall, 30, was forced to withdraw and was hospitalized with what turned out to be a broken left leg.

Unlucky, too, was Davis Love III of the United States, who had enjoyed a practically flawless front nine of 30 and taken his place among the leaders when the sky fell. It took Love eight shots to negotiate the 10th hole, mostly because of a lost ball after overshooting the green, and the quadruple-bogey is the reason Love is six strokes behind.

There were good scores aplenty, however, on a warm day during which golfers who had worn wool ski caps Friday were able to change into short-sleeves. Aside from Baker-Finch’s 64, there were 66s by Nolan Henke, Brett Ogle and Darcy and even sub-70 rounds by Jack Nicklaus and Gary Player, neither of whom are out of this thing.

O’Meara quickly overcame a chunked chip at the 16th hole that cost him a par. At the next hole, O’Meara’s five-iron approach shot left him with a five-foot eagle putt, which he made. Then he sank a 20-footer at the 18th.

Not bad for someone whose muscle spasms were so painful last week that he nearly skipped the trip to England. O’Meara was hurting Thursday, but anti-inflammation medication has since kept him upright.

“I’m 34 and not as young as I once was,” said O’Meara, who learned his trade at Mission Viejo High and Cal State Long Beach. “Orthopedic specialists tell me it’s inflamed cartilage of the rib cage, but I think there’s something else.

“Anyway, they’ll have to drag me out of here to keep me from playing the final round.”

Which is what they actually did to Boxall.

Colin Montgomerie, who was partnered with Boxall and also in contention, said: “Richard was complaining of a pain in his leg walking up six and seven. He shanked a three-iron, missed a few putts and generally was unhappy.

“On the ninth tee, he came through the ball, there was a loud crack and he collapsed on his left side. It was terrible for him and it completely threw me as well. It was difficult to keep my concentration and I dropped a couple of shots myself.”

One player who stayed on the heels of the leaders under difficult circumstances was Darcy, the 39-year-old Irishman who, like O’Meara, has an aching back. He is taking cortisone injections for a disk ailment that recently sidelined him for a month and had him considering a life of retirement with his two Irish setters.

Darcy, best remembered here for making the putt that defeated Ben Crenshaw and the United States in the 1987 Ryder Cup, chipped in at the first hole and putted better than most.

He is tied for second place at 207 with Harwood, one of 11 Australians within nine shots of the leaders. Ballesteros is next, followed at 209 by Mike Reid of the United States and a player who is bringing this tournament even more international flavor, Vijay Singh of the Fiji Islands.

If “anybody’s tournament” is a hackneyed expression, consider this: Nineteen players remain five or fewer shots behind Baker-Finch and O’Meara.

Some of those, including Masters champion Ian Woosnam, who is five back, were anything but happy Saturday with their scores. Woosnam was thoroughly agitated by soft, spongy greens that “are not very good for a major tournament” after missing putts from three feet, two feet and 14 inches, two of which U-turned back toward him after lipping the cups.

Although he still managed a 69, Woosnam said: “I don’t know what the trouble is with the greens. I’m not a greenskeeper. They have been cut down and the short putts are all over the place. You feel you’re lucky to get down in two from 15 feet. They have to do something.”

Nicklaus, eight strokes off the pace, said of the greens: “You watch your partner and his breaks left and then yours breaks right. The greens are too soft and I’m disappointed.”

At least his back and legs are OK.

British Open Notes

After Mark O’Meara and Mike Reid, the ranking Americans are Gary Hallberg, Bob Tway and Fred Couples, all five shots off the pace. . . . Five-time champ Tom Watson shot 72 and is seven back. . . . Phil Mickelson must make up three shots to catch England’s Jim Payne for low amateur. . . . Martin Poxon, another Englishman, is in good position to win the tournament at even par. He has not won a tournament in his 15 years as a pro.

There were nine more eagles at the 525-yard, par-five 17th.

* MIKE DOWNEY: A weekend in the countryside has delivered Ian Baker-Finch to the brink of the British Open championship. C14