Ted Purdy with legendary golfer Byron Nelson in Irving on Sunday. (AP)

Toronto: American Ted Purdy fired a flawless final round five-under 65 to claim a one stroke win over Sean ’Hair and his first US PGA Tour title at the Byron Nelson Championship on Sunday in Irving, Texas.

Twice a runner-up in PGA Tour events, Purdy took the final step into the winner’s circle with a polished last day performance at the TPC at Four Seasons Resort for a winning total of 15-under 265.

He is the fifth first-time winner on the PGA Tour this season.

With only one top 20 finish in 15 events this year, and playing a tournament that featured the world’s top five ranked players, Purdy attracted scant attention when play began.

But he was steady from the start with only one bogey in his final to rounds, accepting the $1.16 million winner’s cheque from 93-year-old golf great and tournament host Byron Nelson.

“It’s just a great game,” smiled Purdy, ranked 173rd in the world. “I played flawless golf. To win on the PGA Tour has been my dream my whole life.

“I’ve been persistent, I’ve been all over the world playing and now I’m happy as hell.

“I just let myself go today and let it happen.”

’Hair, a 22-year-old Tour rookie whose only notoriety had been an overbearing father who made him turn professional before completing high school, began the day with a one-shot lead.

He refused to wilt under the spotlight but settled for a career best second place after carding a final round two-under 68.

With his wife and three-month old daughter watching from the gallery, ’Hair mounted a late rally with birdies on two of his final three holes, including the 18th.

“I played my heart out but Ted is long overdue,” said ’Hair, who has not talked to his father for over two years. “I’m proud of myself and happy for Ted.

“I learned a lot about what it takes to win out there today. It’s not always about making birdies. It’s also about making pars.”

Vijai Singh used an ace on the 195-yard par-three 17th and birdie on the last for a final round five-under 65 to jump into a tie for third with Bob Tway and Doug Barron at 11-under 269, narrowly missing his chance to reclaim top spot in the rankings from Tiger Woods.

With Woods record run of 142 consecutive cuts made coming to an end on Friday, Singh had to finish alone in third or better to take over top spot.

“It doesn’t matter, whatever happens happens, I’m not concerned about that anymore,” said Singh, when asked about the No.1 ranking. “I was trying to win the golf tournament, I had a chance.

“The guys were not really running away.

“I played really well, I just missed a lot of putts out there in the middle of the round. If I had done what I did last week, I would be right in there.”