Phil Mickelson is set for a spell on the sidelines after being forced to undergo surgery on a sports hernia for the second time in three months.

The American initially went under the knife in October after finishing in a tie for eighth at the opening event of the 2016-17 season, the Safeway Open.

However, he has now had to have a second operation on the issue and it is unclear when he will be fit to play again on the PGA Tour.

The 46-year-old’s management group, Lagadere Sports, confirmed the news on Monday evening and said the signs of him making a full recovery were good, but were unable to confirm an expected date for his return.

Mickelson had hoped to feature at the CareerBuilder Challenge between January 19-22 and although he may not be fit enough to play, his representatives said he would be attending the event “at least in his role as tournament ambassador.”

Last season marked a third straight year without a win for ‘Lefty’ but it was not without its highlights.

He was unlucky not to claim a sixth major as he went down to an inspired Henrik Stenson in the final round of the Open Championship while he also claimed two-and-a-half points as the USA defeated Europe in the Ryder Cup.

The Californian’s goal is now likely to be ensuring he is fit for the Masters in April, a tournament he has won three times in his career.

Mickelson is 29.00 to win for a fourth time at Augusta while he is 34.00 to complete the career Grand Slam by finally winning the US Open in 2017.