Double 2015 major winner Jordan Spieth is officially back on top of the world after leapfrogging Australia's Jason Day in the new global golf rankings released Tuesday.

Spieth's tied seventh place in the WGC-HSBC Champions in Shanghai on Sunday was enough to take the Masters, US Open and FedEx Cup champion back to world number one as Day opted not to play to be at the birth of his second child.

Rory McIlroy started the year as number one, but he lost that position to Spieth after the US Open in June and dropped to third after missing the defence of his British Open crown when he injured an ankle playing football.

Day has won six tournaments in 2015, including the PGA Championship in August during a run of four titles in six starts as he reached number one for the first time.

Meanwhile Russell Knox has soared into the world's elite top 50 on the back of his victory Sunday at Sheshan International Golf Club.

The Scot has risen to 31st in the rankings from 85th after picking up the first win in the $8.5 milllon WGC event.

The official world golf rankings are usually released every Monday but were delayed by the late finish at the PGA Tour Sanderson Farms Championship
Source: AFP