Jack Miller's Austin MotoGP weekend got off to a painful start when the Marc VDS Honda rider suffered a big highside in morning practice.

Fortunately the young Australian didn't re-damage the right leg he fractured in winter training and was at least able to ride again in the afternoon, completing 11laps of arguably the most physical track on the 18-round championship.

Miller was rewarded with an improvement in lap time by over a second, although he was still left 20th on the combined timesheets, ahead of only rookie team-mate Tito Rabat.

"It was a real shame to start the weekend off with a big crash like I had this morning," Miller said. "I had a good feeling on the first exit and then put in a new tyre on my second bike and I just didn't generate enough heat in the rear before I started to push.

"I ended up crashing and it is a big shame because this is one of my favourite tracks and I'd already shown I've got some speed here. My right leg is pretty painful and I'll work closely with the Clinica Mobile staff to help make me as comfortable as I can be to try again tomorrow and push hard for qualifying."

Team Principal Michael Bartholemy added: "After a very long journey to Texas we were hoping that today would have a better outcome. Jack had a very big crash this morning and it is clear he is struggling with some pain in his right foot and leg.

"He can only make a few laps and it is not easy for him on a track that is so tough on the body with the changes of direction and hard braking points."