American Phil Mickelson hits from the 18th fairway during the first round of his PGA Tour Champions circuit debut in Branson, Missouri. — AFP/VNA Photo

MISSOURI — Phil Mickelson impressed in his PGA Tour Champions circuit debut on Monday firing 11 birdies in a 10-under par 61 at Ozarks National to lead the Charles Schwab Series event.

Mickelson birdied three of the par-fives on the course at Ridgedale, Missouri, storming home with five straight birdies to lead Australian David McKenzie by one stroke.

Five-time major champion Mickelson became eligible for the Champions circuit when he turned 50 in June. He said earlier this season he didn't expect to take advantage this season as he preferred to keep his focus on the PGA Tour.

But he changed his mind after he missed the cut at the Northern Trust at TPC Boston on Friday and was eliminated from the FedEx Cup Playoffs.

He opened with a birdie, then drove the green at the 350-yard par-four third and was five-under through seven before a bogey at the ninth.

He added another birdie at 11 then rolled in a 20-footer at 13 to launch his closing run – which also included birdie bombs at 15 and 16.

"I had a lot of fun," said Mickelson, who played alongside Retief Goosen and Steve Stricker.

"I enjoyed competing against Retief for so many years and Steve Stricker is one of my favorite people in all of golf. Watching Stricker roll in putts early in the round gets your mindset in a very positive frame and I tried to kind of take his feel and touch and rhythm of stroke and I made some on the back."

Mickelson made it plain after his round that he's now focused on becoming the 20th player to make his debut on the over-50 circuit a victory.

"The expectation is there, but there are a lot of great players out here and it is fun for me to able to compete against them," he said.

South Korean K.J. Choi, making his second start on Champions tour, was in a group sharing third at seven-under along with Rocco Mediate, Rod Pampling and Tim Petrovic. — AFP