Denver: Jarryd Hayne has made such a big impact in the NFL over the past week that opposition coaches are now fielding questions about the former rugby league superstar in press conferences.

Ahead of the San Francisco 49ers' third preseason trial against Denver on Saturday night (Sunday 11am AEST), Broncos head coach Gary Kubiak was asked about the 27-year-old Australian.

"Have you seen much of the rugby player they've got on return?", an American journalist asked Kubiak.

"Yeah I know, he's returning the heck out of kicks right now and doing a heck of a job," he said.

"[He is] tough to tackle. Obviously, he's getting an opportunity and taking advantage of it."

Kubiak will get his first live glimpse of Hayne at a joint practice between the Broncos and 49ers in Denver on Wednesday and Thursday.

It's expected Hayne will see some more time at running back in the third trial against the Broncos at Mile High Stadium when he takes the field against legendary quarterback Peyton Manning.

But Hayne hysteria has gone national in the United States, with those in NFL headquarters in New York City now well aware of the talent looking to crack the 49ers' 53-man roster.

"Jarryd Hayne is a world-class athlete," NFL spokesman Michael Signora said.

"His pursuit of an NFL career with the San Francisco 49ers has captivated fans in Australia and increasingly become one of the most interesting stories of training camp for NFL fans everywhere.

"Fans are attracted to sports for many reasons, and the idea that new fans are becoming interested in our game through Jarryd is something we are very excited about."