* Spieth tucks in two shots behind leader Dustin Johnson
* Twice St Andrews champion Woods struggles to a 76 (Releads with new quotes)
By Tony Jimenez
ST ANDREWS, Scotland, July 16 (Reuters) - Dustin Johnson sounded an ominous warning to grand slam-chasing Jordan Spieth by outmuscling the youngster to power his way to the top of the leaderboard in the British Open first round on Thursday.
The 31-year-old Johnson gave an object lesson in big hitting as he bulldozed his way to a pacesetting seven-under-par 65 in becalmed early weather conditions at the iconic Fife links.
Sharing second place on 66 are fellow Americans Zach Johnson and Robert Streb, South African Retief Goosen, 1999 champion Paul Lawrie of Scotland, England's Danny Willett and Jason Day of Australia.
Spieth, bidding to add golf's oldest major to his wins at this year's U.S. Masters and U.S. Open, tucked in two strokes behind countryman and playing partner Dustin Johnson but is all too well aware of the size of the task that could lie ahead.
"If DJ keeps driving it the way he is I'm going to have to play my best golf to have a chance," the 21-year-old Texan told reporters at St Andrews.
"It's hard to argue with somebody who is splitting bunkers at about 380 yards and two-putting for birdie on five or six of the holes when there are only two par-fives on the course.
"I don't have that in the bag so I've got to make up for it with ball-striking."
While Johnson and Spieth were showing off their dazzling skills, former world number one and twice St Andrews champion Tiger Woods looked a pale imitation of his old self as he slumped to a sad four-over 76.
The 14-times major winner made a wretched start when he dunked his approach into the Swilcan Burn on the first hole and that set the tone for a litany of errant strokes.
"The guys have been shooting good numbers, unfortunately I did not do that," said Woods.
"Hopefully the conditions will be tough tomorrow and I can put together a good round and move up the board."
TURNED TABLES
Woods' prayers may well be answered as the forecast for Friday's second round is for high winds and heavy rain.
Johnson, who suffered U.S. Open heartbreak last month when he missed his eagle effort for victory at the final hole and eventually three-putted, turned the tables on Spieth on Thursday but this was no grudge match.
"We are good buddies and we like playing with each other," said Johnson. "We had a lot of fun out there.
"This venue here is one of my favourite Opens. I really like the golf course and I think it sets up well for me."
The contrast in styles was stark as world number four Johnson belted a series of booming tee shots while second-ranked Spieth relied on strategy, deadly accurate approaches and a magical touch with the putter.
The youngster gave an early statement of his intent by ramming in a six-foot birdie putt at the first.
Spieth, looking dapper in a grey sweater and white trousers, continued to play smart golf and added another birdie at the second.
The American whizzkid, trying to emulate compatriot Ben Hogan who won the year's first three majors in 1953, showed he was human by missing from eight feet at the third before bouncing back with a birdie hat-trick from the fifth.
Spieth picked up another shot at the 11th but needed to caress a curling 20-foot birdie putt into the cup at the last to recover from dropped strokes at the 13th and 17th.
He and Johnson had the advantage of playing early in the day when the weather conditions were ideal for scoring.
The winds started to gust between 18 and 20 miles per hour for the late starters but it did not seem to bother Willett or Zach Johnson as the pair shot up the leaderboard.
(Editing by Toby Davis)