Four days of heat and humility begin this morning in the 2002 U.S. Senior Open at Caves Valley Golf Club in Owings Mills. What stands to be one of the hottest and toughest tournaments in the 22-year history of the Senior PGA Tour has made most in the 156-man field go in wary about coming out weary.

It isn't just the brutal length of the course - at 7,005 yards it is the longest Senior Open not played at altitude - and all the uphill treks on the back nine, particularly the last four holes. It isn't just the way the sun-baked greens might seem more like marble than bent grass.

Nor is it just the fact that major championships, especially the Open, are set up to identify the best players.

In this case, the strongest and fittest both in body and mind - not to mention ball striking and putting - will likely be the next Open champion come Sunday night.

"Just the nature of the Open itself, I think eliminates some players whether physically or whether psychologically, when they see the conditions under which we play Open championships," said Hale Irwin, who has won two Senior Open titles and three regular Open championships. "That could be said year after year."

Irwin, a former All-Big Eight football player at Colorado who at 57 remains one of the fittest players on the Senior Tour, should be one of the favorites this week. But fitness alone won't be the determining factor. If it were, 66-year-old South African Gary Player might be handed the Francis Ouimet trophy and the $450,000 top prize before teeing it up today.

"This is going to be a difficult week," said former Open champion Tom Kite. "The heat, the golf course, the four rounds, the major championship, all of it is going to play a huge role and it's going to be a difficult week for everybody."

The way things have gone this season among the world's best 50-and-over players, there is no clear-cut favorite. Defending champion Bruce Fleisher is still looking for his first win this year. So is Tom Watson, who recently celebrated the 20th anniversary of his historic Open victory over Jack Nicklaus at Pebble Beach.

"You've got to be in good shape," said Watson, 52. "Old guys playing out of a cart [at regular senior tour events], if they haven't been walking the last two or three weeks getting in shape, they may have a problem."

Or, as George Burns said earlier this week: "They should put an ambulance on every tee for these guys - including me."

Certainly at the last four holes, which are considered among the most treacherous on the course and could be Caves Valley's answer to the Black Course at Bethpage State Park, site of the recent regular Open. They start with a 215-yard par-3 and end with a 455-yard uphill par-4.

"They are probably the four best holes I've ever finished on," said Jim Thorpe, who won this year's first Senior major championship, The Countrywide Tradition, in April. "If you can play 15, 16, 17 and 18 even par for the week, you're going to have a chance at winning."

When he was designing Caves Valley back in the late 1980s, Tom Fazio thought about many of the older, more traditional courses in the country that gained their reputation for being tough but fair. He tried to give players a variety of shots to hit, mixing shorter holes with longer ones.

"Certainly the last four holes do have some strength to them," said Fazio, who last year redesigned Augusta National for the Masters. "By blending them with the short golf holes, I felt it was like the old-style golf courses, like Merion. If you play there, it has a reputation for being a short golf course ... but the course gets real long starting on the 14th hole. When you walk off the golf course, you don't feel like you played a short course."

Kite was one of several top-level players who passed up last week's Greater Baltimore Classic at Hayfields Country Club in Hunt Valley to rest up. Others who should be fresh for the test at Caves Valley also include Irwin, Watson, Senior PGA champion Fuzzy Zoeller and Bruce Lietzke.

And then there's Arnold Palmer, who won the 1981 Senior Open in his first try and at 72 will be the oldest player in the field this week. Though he will likely draw the largest crowds - perhaps even bigger than usual now that Nicklaus has withdrawn because of back problems - Palmer is not expected to contend.

That doesn't mean he won't compete.

"I'm still hopeful that I might play some good golf, and I enjoy it. I suppose that's the other thing that brings me here to play," said Palmer, who shot what he called a "generous" 71 Saturday when he played with former Pennsylvania governor Tom Ridge, now the director of Homeland Security, as well as Senior Open chairman Jim Flick.

Whatever he shoots, Palmer doesn't plan on pointing any sweaty fingers.

"When you start complaining about walking in the heat and humidity, the hell with that, just go home and sit in front of the TV and have a beer," he said.