Jason Day has replaced Jordan Spieth as world No1 in the latest golf rankings released on Monday.

The Australian, who won his first major title at the PGA Championship in August, takes the top spot for the second time in his career.

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He previously moved ahead of Spieth on September 21, but lasted just a week as the American won the Tour Championship to regain top spot.

Neither player was in action last week, which ensured that Day would edge ahead based on the rankings formula with 12.42 points average to 12.40 for Spieth.

Former world No1 Rory McIlroy remained in third place on 10.92 points with the new “Big Three” of golf well ahead of the rest of the pack led by Bubba Watson.

Meanwhile, rookie Emiliano Grillo sank a birdie putt on the second playoff hole to outlast Kevin Na and claim his first USPGA Tour title in the season-opening Frys.com Open on Sunday.

The 23-year-old Argentine, who earned his PGA Tour card just two weeks ago by winning the Web.com Tour Championship, fired a three-under 69 – draining a long birdie putt on the 72nd hole to set up the playoff. Grillo, already being touted as rookie of the year contender, said: “I stayed positive, hit a great shot and luckily Kevin made a six. I was just focused on my putt.”