Rory McIlroy and Brian Harman in front after opening round of BMW Championship

The pair lead by one from a six-strong chasing pack which includes England’s Matt Fitzpatrick.

Rory McIlroy watches his tee shot on the second hole during the first round of the BMW Championship (Charles Rex Arbogast/AP) (AP)

Rory McIlroy carded a flawless 65 to share a one-stroke lead with American Brian Harman after the first round of the BMW Championship in Chicago.

The Northern Irishman picked up five birdies without dropping a shot, while Harman split six birdies with a bogey on the par four 12th.

The pair lead by one from a six-strong chasing pack which includes England’s Matt Fitzpatrick.

The 28-year-old dropped shots at the start and end of his opening round, but birdied six of nine holes around the turn.

Meanwhile, Patrick Cantlay has some improving to do if he is to be successful in his bid for a third-straight victory in the BMW Championship.

The American carded a two under 68 on Thursday to sit equal-12th.