The Hayne Plane could be about to fly all over the United States.
"It's a big deal for us here in San Francisco, but it's going to continue to grow if he has the same kind of success in the regular season," Leserth told Newstalk ZB. "If he has that kind of success, then it'll go crazy. It'll go nationwide."
Read more: 'Do I have a job?' - Hayne hears the good news
Read more: Hayne plane soars to new heights
Read more: Code breakers keep the dream alive
Read more: Paul Lasike cut from NFL
The hype, as Leserth explained, has already enveloped San Francisco, spurred on by the 49ers' push for a positive news story after dealing almost exclusively in the negative for the last 18 months.
After making three straight NFC Championship games and losing in the Super Bowl at the end of the 2012 season, San Francisco have since experienced a gloomy time on and off the field. An 8-8 record and the departure of a popular coach has been exacerbated by arrests of some players and the surprise retirement of others.
Hayne, then, represents a win for the the Niners' public relations team, who are keenly capitalising on all the goodwill surrounding the incredible story.
"As someone who's been covering the 49ers for a few years now," Leserth said, "there's probably a great deal of relief and happiness and joy inside the 49ers' headquarters, from the stand-point that they finally have some good news.
"This is a wonderful story for you folks down there and for the 49ers themselves, and I guarantee if you look at the game on [Tuesday], when they open against the Vikings, there will be a ton of No38 jerseys in the stands at Levi Stadium."
If such a scenario seemed infeasible when Hayne stunned the Australian sporting world by announcing his switch almost a year ago, it was still unlikely when pre-season began in August.
Even someone whose career is spent covering the team in minutiae, like Leserth, never imagined Hayne would still be around come the start of the season.
"I think you might have laughed at someone who thought he would have been," he said. "It was a novelty story - a great athlete from another sport with absolutely no experience with American football. [League] is similar with its speed and power and quickness, but there is so much to learn.
"This is stunning."