Smith opened 2020 with an emotional victory at the PGA Tour's Sony Open in Hawaii in January while bushfires raged in Australia.

The 26-year-old raised significant money for Australian charities and dedicated his first individual win on the US Tour to victims of the devastating blazes.

But the Queenslander has failed to kick on, missing the cut in five of the nine events since, with his best result a tie for 22nd.

Coach Grant Field attributes the poor stretch to the fact Smith was already drained when the coronavirus shut down the PGA Tour for 90 days and crippled Smith's momentum.

"Cam hasn't really had a break for two years, so the win in Hawaii was incredible but triggered a deserved rest," Field told AAP.

"The shutdown was an opportunity to take time off but, unfortunately, what comes with that is rust and poor performances.

"If you're competing against the best players in the world you can get caught out if you're not 100 percent sharp."

"History tells us the bigger the stage, the better he is … This is when I expect Cam to fire up.” – Grant Field

However, Sunshine Coast guru Field expects those results to change now the US PGA Championship – starting on Friday (AEST) at San Francisco's TPC Harding Park – launches a rescheduled majors season that includes the US Open in September and the Masters in November.

"History tells us the bigger the stage, the better he is," Field said of Smith, who owns top-five results at the Masters and US Open.

His best result at the US PGA Championship is tied 25th on debut in 2015.

"It's at the point of the season where there are three majors and the PGA Tour playoffs crammed into a short period. This is when I expect Cam to fire up," Field said.

To get Florida-based Smith ready for the majors, Field has been putting in extra video lessons given he can't make the usual trips to the US.

"In the off weeks, we do some live sessions via FaceTime where Cam has the headphones in talking to me while he practises and (caddie) Sam Pinfold films his swing," Field said.

Smith will be joined by five other Australians at the US PGA Championship, including 2015 winner Jason Day, World No.9 Adam Scott, World No.19 Marc Leishman, Matt Jones and European Tour winner Lucas Herbert.

- Evin Priest, Australian Associated Press