Jett Lawrence's streak of 22 straight moto victories has ended in the first round of the SMX Playoffs in Charlotte, North Carolina.
The Australian was quickest in 450cc qualifying but finished the first moto in seventh place.
Lawrence followed up with a second-place finish in Moto 2.
Lawrence's Honda team-mate, Chase Sexton, won both motos.
The recently crowned AMA 450cc motocross champion did not start well in the first moto on the split starting gate and settled into sixth place.
The Landsborough, Queensland native struggled to find a rhythm early and went down eight minutes into the race and fell to 10th place before making up three positions at the chequered flag.
In the second moto, Lawrence again struggled at the start and settled in outside the top 10 before methodically passing riders before finishing second.
Lawrence went into the race on the hybrid supercross-motocross course with no expectations.
“I could be really good at this, or I could be really bad,” Lawrence said. “That's what is exciting.”
450cc top five after Round 1: Chase Sexton 54, Ken Roczen 44, Dylan Ferrandis 40, Jett Lawrence 36 and Jason Anderson 34
In the first 250cc moto, Hunter Lawrence finished ninth after an early fall dropped him to the 22nd position.
17-year-old rookie Haiden Deegan was the Moto 1 winner after starting in third.
Kitchen finished second and Tom Vialle was third.
In Moto 2, Hunter Lawrence, the AMA 250cc motocross champion, again had a poor start and finished in the seventh position after working his way forward from mid-pack.
Japanese rider Jo Shimoda took the race victory after passing Ton Vialle with six minutes remaining in the race.
American Ryder DiFrancesco finished third.
250cc top five after Round 1: Jo Shimoda 42, Haiden Deegan 42, Hunter Lawrence 39, Tom Vialle 38 and Levi Kitchen 35
Round 2 of the playoffs takes place 16 September in Chicago.