I Am Serious has showcased her versatility and reserves of stamina through a compelling finishing burst to the mare's first heavy ground experience at Randwick.

The four-year-old on Saturday racked up her seventh win from 11 starts, and fourth in Sydney since she transferred from veteran Taree trainer and owner Bob Haire, with relative ease.

She levelled up to pacesetter Veladero ($12) and third-placed Bastia ($3.40) at the 100m and loped clear to claim the ATC Owner Benefits Card Handicap (1600m) by 1-1/4 lengths.

Bastia was nosed out of second.

The $2.35 favourite handled a seven-day back-up for the first time in her career with aplomb and had no issues with her first start on a heavy track.

Realising I Am Serious was up to metropolitan class, Haire sent the mare to Chris Waller last year, though he still provides valuable input.

"We talk to Bob and he helps guide us where we're going to go with her. He knew full well she was a city class horse," said Waller's racing manager, Charlie Duckworth.

"She had to dig really deep all the way to the line, which probably means she's going to see further than the mile."

Jockey Tye Angland had only one moment of anxiety before I Am Serious underlined her class.

"I found my spot and then (Aaron) Bullock started to pull back a little bit (on Our Gravano) and he took me out of the race," he said.

"I thought I had too much ground to make up but it just took a few strides."