Next week, of course, is the PGA Championship - the season's final major. He eventually tied for fourth. "It definitely helped", McIlroy said afterwards.
McIlroy has enjoyed huge success with his fellow Irishman on the bag, but it emerged Monday that he could have a new caddie at the WGC Bridgestone Invitational this week in Akron, Ohio.
The 28-year-old hasn't won a major since the 2014 PGA Championship but is considered a heavy favorite for next week's PGA at Quail Hollow in Charlotte. "He kept me positive out there, so that was very much appreciated". The trend was set with the rib injury he suffered in January that would keep him on the sidelines for seven weeks, before a further three-week lay-off in May. He was the best man at McIlroy's wedding to Erica Stoll in April.
Who McIlroy chooses to be his permanent caddie is yet to be known. Fitzgerald was thrust into the spotlight at the British Open last week. McIlroy said in a retelling of Fitzgerald's intervention.
Having picked up his bag not long after he turned professional, the experienced Fitzgerald was the ideal choice for McIlroy starting out, but there have been a number of occasions in recent years when, rightly or wrongly, a finger of blame was pointed in his direction.
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Fitzgerald accompanied McIlroy during his rise to the top of the sport, which included a world No. 1 ranking and four major titles.
The Telegraph reported McIlroy's caddie at the next two tournaments will be Harry Diamond.
Phil Mickelson split with caddie Jim "Bones" Mackay last month after a 25-year partnership that netted the American five majors.