Johnson holds clubhouse lead at Boston

Johnson, fresh off his win over Jordan Spieth in the first leg of the PGA Tour's four lucrative playoff events, fired a five-under-par 66 at TPC Boston that left him one shot clear of fellow American Kyle Stanley and Australian Marc Leishman.

Swede Jonas Blixt carded a 68 to lie a further stroke adrift at three-under, level with Americans Jason Dufner, Kevin Na, Luke List and Brian Harman.

U.S. Masters champion Sergio Garcia was three under through his first eight holes.

Johnson, who is finally showing the form he displayed before injuring his back while falling down stairs on the eve of the Masters in April, started on the back nine and used a superb approach from 221 yards to set up a four-foot putt for eagle on the par-five 18th hole to reach the turn in four-under 31.

The long-hitting American, who leads the FedExCup standings after winning the series opener, mixed a bogey with two birdies over his next four holes before a steady finish.

British Open champion Spieth, who failed to close the deal last week despite holding a five-shot lead in the final round, bogeyed three of his opening seven holes but used birdies at his 13th and 16th holes to get to one-over-par 72.

Defending champion Rory McIlroy was one under through nine holes.

This week's field features the top 100 players in the standings. The top 70 after Monday's final round advance to the penultimate event to be played Sept. 14-17 at Conway Farms in Lake Forest, Illinois. (Reporting by Frank Pingue in Toronto, editing by Gene Cherry)