Sports

Rory McIlroy opens with a 71, 4 shots behind clubhouse leader Robert Karlsson

  • World number one Northern Ireland's Rory McIlroy plays out of a bunker during day one of the 2015 BMW PGA Championship at the Wentworth Golf Club, Virginia Water,  England Thursday May 21, 2015. (Adam Davy/PA via AP) UNITED KINGDOM OUT

    World number one Northern Ireland's Rory McIlroy plays out of a bunker during day one of the 2015 BMW PGA Championship at the Wentworth Golf Club, Virginia Water, England Thursday May 21, 2015. (Adam Davy/PA via AP) UNITED KINGDOM OUT  (The Associated Press)

  • Northern Ireland's Rory McIlroy plays a shot during day one of the BMW PGA Championship at Wentworth golf club, Virginia Water, England, Thursday May 21, 2015. (Adam Davy/PA via AP) UNITED KINGDOM OUT  NO SALES  NO ARCHIVE

    Northern Ireland's Rory McIlroy plays a shot during day one of the BMW PGA Championship at Wentworth golf club, Virginia Water, England, Thursday May 21, 2015. (Adam Davy/PA via AP) UNITED KINGDOM OUT NO SALES NO ARCHIVE  (The Associated Press)

  • Northern Ireland's Rory McIlroy waits to play with his caddie JP Fitzgerald, right, during day one of the BMW PGA Championship at Wentworth golf club, Virginia Water, England, Thursday May 21, 2015. (Adam Davy/PA via AP) UNITED KINGDOM OUT  NO SALES  NO ARCHIVE

    Northern Ireland's Rory McIlroy waits to play with his caddie JP Fitzgerald, right, during day one of the BMW PGA Championship at Wentworth golf club, Virginia Water, England, Thursday May 21, 2015. (Adam Davy/PA via AP) UNITED KINGDOM OUT NO SALES NO ARCHIVE  (The Associated Press)

Rory McIlroy opened the defense of his BMW PGA Championship title on Thursday with a 1-under 71 that left him four strokes behind clubhouse leader Robert Karlsson.

McIlroy says "I felt like I left a couple of shots out there" and that "I did not do anything that good and there is definitely room for improvement over the next few days."

Karlsson made six birdies for a round of 67. The Swede birdied two of the final three holes to take the overall lead.

Miguel Angel Jimenez, Jorge Campillo and Chris Wood were a shot back on 4-under.