Already booked to ride Newcastle Cup runner-up Attention Run at 50 kilograms in The Metropolitan (2400 metres) at Randwick, the 41-year-old was also on standby for the Chris Waller team for the $1 million Epsom Handicap (1600m).

After the 20-horse Epsom field was finalised on Tuesday, Waller had six runners, and lightweight jockeys were in demand with 15 starters to carry 51kg or less.

Gibbons, who got down to 50kg to ride Violate in the Doncaster in April this year, was given the job on $51 chance Kaonic, which drew barrier eight.

"I've been sitting on this for a week, knowing that I'm a chance of being in them, but I wasn't sure if they'd get runs," Gibbons said.

"They booked me for the Epsom but they told my manager it was all pending on what horses got runs. If a few fell away, I was probably the first one who would have missed out, but it's ended up all right.

"He's drawn well and has no weight, and you just never know in those races."

Gibbons has not ridden either horse in a race but has trialled and worked Attention Run, which put in a bold front-running effort to finish second as a $13 shot in the group 3 Newcastle Cup on September 20.

The mare has gate 11 for The Metropolitan and Gibbons was excited about the $21 hope's prospects.

"Her run was outstanding," he said.

"She probably went a bit keen early and probably wasn't entitled to hang around and run second.

"I think her run was probably the pick of all of Kris's horses in the Newcastle Cup. She drops in weight and I've sat on her a few times since, and had a main gallop on her this morning, and she's absolutely flying.

"It's never easy to win those races, but the Metrop the last few years, the light ones are winning, so I'm in with a show."

Gibbons usually rides as low as 54kg and he faces a tough task to make weight for Saturday. However, he was confident after dropping to 50kg already this year .

"I found last time I wasn't too sure how early I should start cutting things out, and it's made it a bit easier this time knowing that," he said.

"When Kris first mentioned it to me three or four days ago, I was 54 and a half. I got home from the track this morning and I was 53, so I've got another four days to take off another three.

"I'd always planned that today and tomorrow would be the days I really cut everything down. I've already lost that 1.5 just by eating the right stuff and from here on in it's just cutting the sizes down, and from Friday I'll be cutting the fluids down."

Gibbons is working with personal trainer Alison Morgan in his home suburb of Chisholm and plans to get to Randwick early on Saturday to use the hot spa to shed the last of his weight.

His best result from a handful of group 1 rides has been a half-length fifth aboard Hera in the 2015 Coolmore Classic. A breakthrough victory would cap a memorable run for Gibbons, who rode a career-best 137 winners last season and claimed the Newcastle premiership. He has also recently become engaged to partner Keeley Gageler.

"Add a group 1 to all that, it would make it pretty special," he said.