Logistics prevented that, but new World No.2 Thomas reflected the players' wide support when he dedicated his four-shot victory to Australia's ailing former PGA Tour player on Sunday.

Lyle last week ceased treatment and began palliative care amid a third battle with acute myeloid leukaemia.

"This win, and this week, was definitely for Jarrod," Thomas told AAP.

"I wanted that yellow hat and I asked (equipment manufacturer Titleist) if we could get some, but everything in stock was sent to Jarrod (in Australia), which is understandable.

"But I was glad we could get the yellow ribbons to show some appreciation."

Thomas carded one-under-par 69 at Firestone CC to reach 15 under and finished four shots ahead of Kyle Stanley (68), while World No.1 Dustin Johnson and Thorbjorn Olesen (both 64) tied for third at 10 under.

Adding to the emotion of 25-year-old Thomas' victory was the joy of having his grandparents, Paul and Phyllis Thomas, in the gallery.

Paul and Phyllis Thomas witnessed their grandson’s ninth victory on the PGA Tour. PHOTO: Sam Greenwood/Getty Images.

Paul was a career club professional and played at Firestone in the 1960 US PGA Championship, missing the 54-hole cut.

"I got a little choked up when I looked over and saw my grandpa and grandma," Thomas said.

"This is my first PGA Tour win with him here and it's really special.

"My grandpa is not emotional, but I hadn't seen him smile or be that happy, maybe ever."

Thomas' ninth title on the US Tour, and second this year, earned him $US1.7 million and moved him up one spot on the rankings to World No.2.

Thomas will take enormous confidence into his PGA Championship title defence this week as he seeks a second major title.

"To win on a championship golf course like (Firestone) and against a very tough field, it just felt great," he said.

Evin Priest, Australian Associated Press