The world number one from Holywood hit seven birdies to carry him into a tie for third place on 10 under, two shots behind leader Russell Henley of America.McIlroy, who has won three of his last four competitions, made a fantastic start in Boston on Sunday with birdies on holes two and three.The 25-year-old then went to three-under at the seventh after driving a 132-yard approach to nine feet and holding his nerve to make the putt.More birdies followed on the 10th, 13th and 15th and Rory was inches away from acing the 16th - but was nevertheless able to tap in to go seven under for the day, leaving him well and truly in contention for a chance to add to his recent Open, WGC-Bridgestone and US PGA victories."I converted some more of the chances that I gave myself today," the Ulsterman told Sky Sports."I was pretty frustrated coming off the golf course in the last couple of days because I felt like I left a lot of shots out there."Even today, I felt like I might have left a couple out there, especially on the last. But I'm happy with how I converted those chances and I'm going to need to do the same tomorrow if I'm going to win."