The Ulsterman and the defending champion have been drawn together in the first two rounds at Bellerive in St. Louis along with four-time champion Tiger Woods.
McIlroy also played with the new world No.2 in the final group of the WGC-Bridgestone Invitational when Thomas took a three-shot lead into the final round. But while the four-time Major champion suffered another Sunday letdown with a three-over-par 73 to finish tied sixth, Thomas showed his steely determination with a solid 69 to win by four shots.
Like McIlroy, Thomas had not triumphed since March. “I mean, it feels like I haven’t won forever,” he said.
But the 25-year-old showed the killer instinct that Northern Irishman has also lacked this season in his final rounds at the Masters and the Open.
McIlroy, who lives near Thomas in South Florida and often practices with him, said: “I like JT’s attitude over everything else.
“He’s got a nasty streak in him, which I think you need out here. He has that. When he gets himself in the hunt, you can see like a little twinkle in his eye and he really enjoys it.”
Unlike McIlroy lately. He smashed one 420-yard drive in his final round at the Firestone Country Club but hit only four out of 14 fairways – and is ranked No.124 for putting on the PGA Tour.
Thomas won six times in 2017 – including his first Major – but had recorded only two top-10 finishes in March, so he called a crisis meeting with his caddie Jimmy Johnson and his father and swing coach Mike.
“We sat down and just said, ‘What are we doing wrong? What can we do better?’” said Thomas Snr. “He initiated it, he said this what he wanted to do. I told him, ‘That’s really mature of you. When I was 25 years old I wouldn’t have done that’.”
McIlroy, who has won once since his April 2017 marriage, needs another similar bout of introspection before he bids to reclaim a first Major since the 2014 US PGA. At Carnoustie, he closed with a 70 to finish two shots behind Francesco Molinari.
He said: “It was a very strange Sunday. I think for me it was good, because I definitely didn’t have my best stuff that week and I still had a chance to win. So that was a positive, knowing that even if I don’t feel like I’m swinging it my best or I don’t have everything quite under control, I can still find a way to give myself a chance.”
McIlroy has won the US PGA twice and decided not to visit Bellerive in advance to practice on a course which has not held a Major since 1992.
“I was in Florida last week, I contemplated going over to Bellerive for a day and checking it out, but I told myself I’ve never done it before for a PGA and I’ve won it a couple times and I played well, so why would I change what I’ve always done?” said McIlroy.
“I’ve always felt less pressure at the PGA because it’s a golf tournament that I’ve always felt comfortable at.
“I don’t need to change my game, I don’t need to try and, manufacture different shots. “I think I can go with what I have and know if I do that well, I’m going to have a good chance. I’ve always felt like it’s my most comfortable major, and I think the results back that up.”
Woods finished with weekend rounds of 73-73 – his worst performance at Firestone since 2010.