Seems like a long time ago now that Lowry and McIlroy were playing golf together as teenagers. Now it was the Irishman's turn for a chance in the limelight as he dethrones the World Number One of his WGC Title at Firestone.
The Irishman was sitting in third place after 54 holes, two shots adrift of co-leaders Justin Rose and Jim Furyk.
However whilst both of them slipped up with over par rounds, Lowry went on to shoot 66 to claim his maiden American Title, two shots clear of Bubba Watson.
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Dreaming over Coffee
On Sunday, the two time winner on European Tour was mulling over what it would be like to become a three time tour winner, sitting in a Starbucks!
"(You) just think about lifting that trophy on the 18th green," Lowry said, "Then when I'm in a good frame of mind, I let myself do it, and I give myself a little slap in the face and say, right, you need to get back to work, back to doing what you do best."
It was some impressive feat to be able to go bogey free round Firestone, with its narrow fairways and juicy rough, but it also required some masterstrokes from the Irishman. Two birdies came from two different shots which had to be hit over the towering fir trees that separate the holes at Firestone.
Long Time Coming?
Despite being three years the senior to current the world No1, Lowry hurled himself into the limelight back in 2009.
As an amateur, he managed to win on the European Tour at the Irish Open, holding off Robert Rock in a playoff.
At the time, the Irishman had proclaimed to the World that he would stay an amateur until after the following Walker Cup, but a change of heart and reflection lead him to turn professional one week after his triumph.
It seemed like it could have been the wrong choice, but six top ten results across 2010 and 2011 seasons was followed up by a win at The Portugal Masters.
His career would be topped off now by winning on American Soil, having been the first non-PGA Tour member to win a WGC since Martin Kaymer in 2011.
There is obviously a rivalry between the 2014 and 2015 winners of the Bridgestone Invitational at Firestone.
Things have changed since those days of course. The Northern Irishman doesn't have crazy hair anymore and is in the shape of his life, where the Irishman has a great big bushy beard.
However, when asking whether this victory was that little bit sweeter, having taken the crown from McIlroy.
"I don't care really who won it last year," Lowry said, chuckling. "I won it this year, and that's all that matters to me right now." reports PGA Tour