The Holywood man hit five birdies to move out in front, however late bogeys on two of his last three holes saw him finish joint top with Jordan Spieth and Gary Woodland on 67.McIlroy, who is chasing a first FedEx Cup title, said he left the Cherry Hills course in Colorado feeling slightly disappointed after making such a good start to his round on Thursday."You can see by the scores it's pretty tricky out there," he told Sky Sports. "Low scores aren't really too easy to come by so 67 is still a good start even though it could have been a bit better."The fairways are firm so even when you're hitting irons and fairway-woods off the tees they're running out and through fairways and into the rough and the rough is thick."Then the greens are so firm, the greens have got so much firmer over the past 24 hours and it's really made a huge difference."Meanwhile fellow NI golfer Graeme McDowell made it to three over with one to play, when frustratingly, play was suspended due to poor weather.