Dale Begg-Smith has retained his number one world ranking despite missing the podium by one place in a World Cup in Inawashiro.
The Olympic champion extended his lead over nearest rival Guilbaut Colas by 26 points, the Frenchman only managing 11th place in the Japanese event.
With two events remaining in the season, Begg-Smith leads the World Cup title chase on 384 points, 43 points clear of Colas.
Nathan Roberts, the Inawashiro winner, is in third place on 325 points.
In the first of two events scheduled for the weekend, Begg-Smith qualified in second place behind Roberts, earning 24.85 points to the US skier's 24.95.
In the final, the Australian was one of the slowest down the course, and his usual impeccable turns ranked only fourth of the finalists.
Roberts took the gold medal with a points score of 25.78.
US team-mate Jay Bowman-Kirigin claimed the silver with 25.75 points, his first podium coming in his sixth World Cup event at the age of just 19.
The bronze went to the oldest man in the field, Japanese skier Yugo Tsukita, on 25.14 points.
Begg-Smith's fourth placing came with 24.48 points.
A dual moguls event will be contested today, Sunday February 18.
Also in Japan, Damon Hayler and Alex Pullin have both finished in the top twenty of a snowboard cross event in Japan, Pullin surprising by qualifying for the final rounds in fifth place.
Nineteen-year-old Pullin finished in 18th place in his first World Cup outing, while Hayler won his way through the first round of finals to finish in 11th place overall.