JEREMY RANCH - For the seventh time in seven summers, the PGA Senior Tour is in Utah again this week for the Showdown Classic at the Jeremy Ranch Golf Course. But it isn't the same old gang. If one thing's obvious as the Encore Tour becomes an established part of the American sports scene it's this: You can't tell the players without a program anymore.

What started out as a two-event tribute-to-nostalgia golf tour in 1980 has emerged into a 37-event, $10.5-million ultra-competitive Senior Tour in 1987. The guys you heard of are being joined by a lot more guys you never heard of.It's like Miller Barber said after shooting an opening round-70 yesterday, "It used to be more of a party out here. There's not so much of that anymore. Now it's serious. Now it's mostly golf."

Not that the unflappable Mister X is complaining. Hey, it's a living. Since joining the fledgling Senior Tour in 1981 Barber, no matter who he's been paired with, has won 22 tournaments (including the Jeremy Ranch event twice) and more than $2 million in official money.

"It's a lot more competitive now than it was," Barber said. "Our tour has lost a little of the old glamor. Now it's another golf tour is all. But that's fine - just go out there and see who can beat who. That's what it's all about."

The Senior Tour has become so successful, and expanded, that on any given week a number of the legends of the past are doing like they used to do on the Regular Tour - they're taking the week off.

Despite having the third biggest purse ($450,000) on the '88 Senior Tour, the Showdown Classic is experiencing major no-show-itis this week. Billy Casper, Arnold Palmer, Don January, Gary Player, Chi Chi Rodriguez, Bob Charles - none of them are here.

To drop a few names.

But that doesn't mean there isn't, as Miller Barber suggests, some serious golf going on - or that just because the player on the tee didn't win the Masters four times and didn't once share a motel room with Ben Hogan doesn't mean he can't shoot under par.

Ten million dollars in prize money has a way of attracting contenders from all walks of life. The Showdown's first round yesterday was a case in point. Of the 19 pros who shot par or better, at least half of them could sit down next to you in an airplane, or join your foursome on the first tee, and you'd say the same thing the galleries were whispering, "Who's that?"

Leading the tournament is Ben Smith, a reformed auto mechanic who never played on the Regular Tour but who didn't let that get in the way of shooting a 6-under-par 66.

In second place, at 68, is Jim Cochran, a club pro from Missouri who has no Regular Tour credentials either.

Smith and Cochran played in the same group yesterday. They competed in relative peace and quiet until they got to the last couple of holes, when word spread about their exploits, after which they poised over putts while the galleries whispered, "Which one's Smith?" and "Which one's Cochran?"

Some of the other first-day par-busters included one Bob Rawlins, a Senior Tour rabbit (non-exempt player) who was the 1984 Senior Amateur champion, and Gordon Waldespuhl, who didn't play on the Regular Tour until he turned 45. Shooting even par were Quinton Gray, who joined the Regular Tour in 1977 and played briefly but never won any money; Dick Hendrickson, who quit his job as a head pro in Pennsylvania to join the Senior Tour this year as a rabbit; Walter Zembriski, a former steelworker; and Dick Rhyan, a qualifying school graduate from last fall.

Mixed in with the above golfing newcomers were such as five-time British Open champion Peter Thomson, 1969 U.S. Open champion Orville Moody, 1968 Masters champion Bob Goalby, 1971 Masters champion Charles Coody, and Gene (The Machine) Littler, 29 times a winner on the PGA Tour.

So there were a few reputations holding their own out there - alongside the auto mechanics, lifetime pro shop merchandisers, and steelworkers.

But the list varied widely from the top finishers of the first Jeremy Ranch Senior's event held in 1982. Billy Casper won that tournament, followed by Don January, Miller Barber, Gene Littler, Julius Boros, Paul Harney, Bob Goalby, Gay Brewer, Peter Thomson, Dick Mayer, Jerry Barber, Guy Woolstenhulme and Sam Snead.

Introductions were not necessary back then. Those 13 men had no less than 242 Regular Tour victories among them - compared to just 62 for the 19 players who shot par or better yesterday.

When the tournament was over in '82, they held a Hall of Fame party. After Sunday's final round this week, they'll hold a financial affairs meeting and disperse quickly - either for next week's event in Newport, Rhode Island, or for a week off.