Jason Day in trouble as Jordan Spieth and Phil Mickelson appear at Pebble Beach

Australian Jason Day struggled to gain ground on day two of Pebble Beach's Pro Am, leaving Phil Mickelson and Jordan Spieth behind.

After the start of the second round, One failed to record a single bird at the top of the first nine at Spyglbad Hill.

The former world No. 1 aggravated his troubles with a boguey at eighth of the normal-4, falling to five under par and six shots to the head.

American Scott Langley (through 13 holes) sets the tone at 11 under, with the triple big winner Spieth.

READ MORE:
* The American golfer drank on the course
* Courses in New Zealand in the world's top 10
* Childish Garcia needs to "grow up"
* The incredible Saudi collapse of Garcia

Mickelson, five-time champion, is about to finish his round and is tied for third with Lucas Glover and British veteran Paul Casey.

The day is tied for the best Australian on Friday with the young Curtis Luck, who found his way back into the fight race with five birdies and a bogey.

Aaron Baddeley (Pebble Beach Golf Links) is the next best Australian with three cents, while countrymen Adam Scott, Cameron Davis, Ryan Ruffels and Matt Jones are sitting on two cents.

Queenslander John Senden is tied while compatriot Rod Pampling (77, Pebble Beach) dropped to five out of five.

At Pebble Beach Pro Am, 156 professionals compete in an official US PGA Tour tournament alongside a team competition with 156 amateur partners. Each group has two professionals and two amateurs.

The event takes place on three courses: the Pebble Beach Golf Links, the Spyglbad Hill and the Monterey Peninsula Country Club.

The first three days, two-man teams play the best ball format. A 54-hole cup is made and the final is played at Pebble Beach.

The event has gained worldwide fame because of its large number of celebrities.

This year's top surfers are Kelly Slater, NFL star Aaron Rodgers and comedian Ray Romano.