— As soon as you step to the first tee of a major golf championship, an entirely new nervous system takes control of your body. Unfortunately, it is often your old nervous system — even if you are Tiger Woods at the Masters.

The experience is especially traumatic if that previously ingrained motor memory was taught to you by your current nemesis: swing-guru turned tell-all author Hank (“The Big Miss,” available on Amazon) Haney.

Whatever you’ve been working on, drilling into your numb skull, suddenly disappears with the dawn; you find yourself deep in the left woods off the first tee. Then, suddenly, you’re taking a drop in the jungle at No. 2. Who’s hitting these shots? What gremlin has inhabited your body? Then, before you know it, you’ve snapped your tee ball so far left at the ninth that you’re suddenly playing the first. Again.

We all know these helpless feelings at our own humble levels of the game. The “new” seems so easy on the driving range. But step to the tee and that old original-sin swing you thought you’d divorced forever — that Dreaded Ex — is right back in your bag.

But in the first round at Augusta National it was Woods who felt that panic, as if another being had inhabited him. From those first two hooks to his bogey-bogey finish, including a penalty stroke after his drive at the 18th, Woods battled with himself and the memories bequeathed to him by Haney as well as muddy, stinky Augusta National.

Call the day a bloody 18-hole draw — an even-par 72 that left Woods well behind many fine players, in a 16-way tie for 29th place, but still within five shots (gulp) of former world No. 1 Lee Westwood. Somebody should have rung a bell and wiped off Tiger’s head covers every time he stepped to the next tee. Because Haney, ready to jab his synapses and hook his neurons, was waiting every time Woods took out his driver.

“Same old motor [memory] issues,” Woods said after five wild hooks and three mud balls when he finally found fairways and squandered an opportunity at a fine round after he reached the 13th tee — the place to start a charge — at a tempting 2 under par. “It was the Hank backswing with a whole new down swing.”

You don’t even have to play golf to know that won’t work. Walk downstairs, but think really, really hard about how you are doing it. Welcome to the emergency ward.

The professional gamblers of the golf universe installed Woods as the favorite at this Masters. They apparently have no idea just what an enormous job lies ahead of Woods before he can win another major title. As a corollary, we probably won’t grasp what an amazing achievement it will be for Woods when he finally does it. How many different brain lobes can be in fundamental transition at once?

Tiger won a full-field PGA Tour event for the first time in 30 months just two weeks ago at Arnold Palmer’s backyard barbecue in Orlando. How nice. “Tiger is back,” many said. Back as a Tour winner, sure, where modest-speed greens merit minimal glory. But such tests, no offense to Arnie’s track, bear about as much resemblance to winning the Masters, where every nerve is tested and every shot is menaced by your own subconscious, as a pair of Mouse Ears do to a tuxedo.

What Woods faced here on Thursday — the need to have a swing that he can trust on Sunday afternoon on the back nine when every iota of his competitive being is electrified with the desire to win — will not go away until he has actually won his first major since The Fall.

Where is he in the pursuit of that agenda? Right now, he has a swing that works for 72 holes at Bay Hill but can’t even get him to the first fairway in one piece at Augusta.

The pressures and anxieties of the first round at the Masters have always unsettled Woods. In his last 10 Masters, he has shot a crummy 3 over par on Thursday (usually a good scoring day) while posting a spectacular 46 under par on Friday-Saturday-Sunday. That Thursday hex, more than any other one reason, explains Woods’s string of excellent, but frustrating finishes since ’02, including T3, T2, 2, T6 and T4. Once, he overcame an opening 74 to win in ’05. But Thursday remains Woods’s self-imposed handicap — only one first-round score in the 60s in all of his 18 Masters.

Woods will battle here. He always does. But his whole career has been a testament to an unparalleled gift for front running, not coming from the pack. Now, he’s chasing again, and just when he thought he’d come here with his game almost entirely intact.

“I certainly am excited. I’m driving the ball much better than I have. I’ve got some heat behind it and it’s very straight,” Woods said on Tuesday. “My iron game is improving. So everything is headed in the right direction at the right time.”

Except for one small factor: This is a major. After all his self-inflicted agonies and multiple knee-ankle injuries, after his swing changes and life changes, the only thing that matters to him is to take the last huge step back to a major throne. What stakes could be comparable?

Psychologists say if you are born speaking another language, say German, then move to a different country as a child and become fluent in that language, then decades later awaken in the night in a burning house, you will scream “Fire!” in German.

So, the battle Woods waged on this soppy wet course, where the pedestrian pathways smelled like a pig sty, is a kind of golf combat he will face over and over — but probably only in majors, the only events that feel as intense to him as a house afire in the night.

“I just fought my way around and grinded. I got about as much out of it as I could,” said Woods. “I could maybe have gotten one, maybe two shots lower.

“I hit it well warming up, then . . . ,” Woods said.

Then he stepped to the first tee of the first major championship — since he’s gotten himself back together — and found himself in the grip of the same swing he had before he ever immortalized a fire hydrant.

“I’m excited. I can take some positives out of it for tomorrow,” said Woods, fortunate that microphones and tape recorders are not polygraphs.

So, all happy and excited for the ’morrow, where are you going now? Big steak?

“As soon as I can get away from you guys, I’m going to the range,” Woods said.

And 17 seconds later, he did.

For Thomas Boswell’s previous columns go to washingtonpost.com/