OHIO (REUTERS) - Rory McIlroy sacked his caddie of nine years after growing tension in their relationship caused the four-time Major winner to question his own behaviour on the golf course, he said on Wednesday.
McIlroy parted company with J.P. Fitzgerald last week after the British Open and will have his best friend Harry Diamond on his bag for the next two weeks.
"Player/caddie relationships have their ups and downs. There was probably a few too many of those over the past year or so," McIlroy told reporters in Ohio on the eve of the World Golf Championships Bridgestone Invitational.
"It was one of those times I felt I needed to mix something up a bit ... It was just a build-up of stuff that I felt I needed to make that change."
McIlroy, who won his last Major at the 2014 PGA Championship, employed Fitzgerald in 2008 shortly after turning professional.
After a slow start - McIlroy missed his first three cuts with Fitzgerald on the bag - the pair enjoyed a brilliantly successful partnership as McIlroy took over from Tiger Woods as the game's dominant force and became world No. 1.
At the British Open at Royal Birkdale two weeks ago, McIlroy heaped praise on Fitzgerald, who delivered some blunt words to his boss after the Northern Irishman started the tournament with a string of bogeys.
After fighting back to shoot one-over 71 in the first round, McIlroy told reporters that Fitzgerald had done a "great job".
McIlroy eventually finished equal fourth in what turned out to be the swansong for his caddie.
"You spend so much time with someone that the little things can annoy you," McIlroy said.
"Nine years is way longer than the average. We didn't get off to the best of starts. He took a bit of a risk on me as well, showed a lot of loyalty and I felt I repaid that...
"I still consider J.P. one of my closest friends but sometimes to preserve a personal relationship you might have to sacrifice a professional one.
"I was getting very hard on him on the golf course and I didn't want to treat anyone like that, but sometimes this game drives you to that."
The 28-year-old said he decided to use Diamond this week at Firestone Country Club and at next week's Major, the PGA Championship in Charlotte, because he was looking for familiarity.
He has not made a long-term decision about who to use after that.
"I just needed someone that knew me and that's why I took Harry for the next couple of weeks," McIlroy said. "He knows my game, my personality...
"It could be two weeks. It could go longer than that. That decision will be up to Harry. He's got his own (business) back home but a couple of wins could change things."