Rory McIlroy carded an opening round of 68 to lie four shots behind joint-leaders Patrick Reed and Alex Noren at the Farmers Insurance Open.

McIlroy had five birdies in his round, with the only dropped shot coming at the 15th. He stands at four under, alongside ten other players.

Reed started strongly while Noran finished well as the pair took the opening-round lead in California.

Starting his tournament on the back nine, American Reed was locked in from his opening drive, stringing together three straight birdies before adding a fourth on the 17th to head into the turn at four under.

He then picked up another four shots on the back nine to finish Thursday's opening round with a bogey-free score of eight-under 64.

Reed shares a one-shot lead with Sweden's Noren, who also started on the North Course's back nine.

Noren birdied the 10th and 14th before soaring up the leaderboard with an eagle on the 17th.

A bogey on the next hole threatened to derail his momentum, but Noren recovered well to add five more birdies on the front nine.

Trailing the pair is American Scottie Scheffler, who finished seven-under on the back of five birdies and an eagle on the 16th.

It wasn't a great day, however, for the other Irish competitor Seamus Power. The County Waterford native posted a 78 to lie at six over.