Australian pair Jason Day and Matt Jones shone in the Californian sun on Friday with red-hot second rounds at the US PGA Tour’s Pebble Beach Pro-Am.

Jones carded a six-under 66 to sit at the top of the leaderboard with Brandt Snedeker at 12-under for the tournament.

An ill Day, who won last week’s event at Torrey Pines, made up for a pedestrian 72 in the opening round by firing a nine-under 62 on the Monterey Peninsula course to move to three shots from the lead.

It was Day’s equal-best Tour score as he collected eight birdies and an eagle against just one bogey and was one shot off the Monterey Peninsula course record, set by Charlie Wi with a 61 in 2012.

Day’s move into contention was all the more impressive since the 27-year-old thought a stomach ailment might prevent him from teeing off.

Day said he thought he caught a bug from his young son Dash, who was so ill earlier this week that his parents took him to a hospital emergency room.

“He had some stomach problems and he was throwing up,” Day said.

“And then he gave it to my wife and then my wife gave it to me. So I didn’t think I was going to play today, especially 30 minutes before my round because I was feeling pretty awful.”

“To be able to shoot nine-under out there with how sick I was, thinking about pulling out, was pretty special.”

Jones and Snedeker – who both played the Spyglass Hill course – lead by one stroke from Justin Hicks (68) while nine Americans and Canadian David Hearn are a shot further behind at 10-under.

John Daly, who started the second round one shot behind the lead, signed for a 72 to be at six-under.

The field will be reduced after Saturday’s third round, after every player has tested each of the three courses in use over the first three rounds – the par-72 Pebble Beach Golf Links, par-72 Spyglass Hill and par-71 Monterey Peninsula.

If Day wins the tournament, he will supplant Henrik Stenson as world No.2 behind only Rory McIlroy.