Spieth struggles to maintain form

Overnight leader Jordan Spieth was tumbling down the leaderboard on the third day of the Farmers Insurance Open after dropping four shots.

A stunning round of 63 included nine birdies and left the 20-year-old American on 10 under for the Californian tournament heading into the third round.

But bogeys on the first and fourth holes, and a double bogey on the par-four fifth, saw him slip out of the leading positions while Marc Leishman made his move.

The Australian found a birdie on the fifth to reach eight under and therefore a share of first place midway through Saturday's action. Belgium's Nicolas Colsaerts made par over his first five holes to check Leishman's progress.

Also in good touch are Scott Stallings - the Massachusetts man mixed three birdies with a bogey over the front nine to close within a single stroke of the top two - and Gary Woodland of Kansas.

Keegan Bradley found birdies on the sixth and eighth holes to breach the top 10 and sit alongside the likes of Pat Perez, Morgan Hoffman and Jason Day.

It was, however, turning into a day to forget for Tiger Woods.

The world number one just made the halfway cut by a single stroke and tumbled right out of contention with a run of two double bogeys and then two bogeys over four successive holes.