Nicky Hayden will miss the two-day winter test at Jerez this week after suffering a twisted knee while flat-track training last Friday.
The former MotoGP world champion, who joined the Honda World Superbike squad at the start of 2016, has returned to the USA to undergo further medical tests to uncover the extent of the injury and a plan of recovery.
As a result, Hayden's new team-mate Stefan Bradl will be the sole rider for the Ten Kate Honda squad at the Jerez test after his debut for the squad at Aragon last week.
With the winter testing schedule set to wind up on the 21st December until its restart in 2017, Hayden's injury could potentially mark the end of his testing duties until the new season on the all-new CBR1000RR Fireblade SP2.
A host of World Superbike teams are testing throughout the week at Jerez, including the factory Yamaha, Kawasaki and Ducati squad plus the new-look factory Milwaukee Aprilia squad with Eugene Laverty and Lorenzo Savadori. A number of MotoGP teams are also testing at Jerez.