Breaking news here late tonight: Honda has announced Jett Lawrence suffered a thumb injury in a practice crash yesterday that will require surgery and force him to miss the remainder of the AMA ProMotocross Championship. His injury will require surgery and his goal is to return at the first SuperMotocross World Championship (SMX) playoff round in Norrh Carolina. 

The Full press releae from Honda:

Jett Lawrence to Miss Remainder of AMA Pro Motocross With Thumb Injury

Torn UCL incurred in a practice crash this week
Lawrence to undergo a procedure on Thursday
Goal is to return for SuperMotocross title defense

DADE CITY, Florida – Having injured his thumb in a small practice crash Tuesday, Team Honda HRC rider Jett Lawrence will undergo a procedure this week, which will result in him sitting out the remainder of the AMA Pro Motocross series.

The fall took place on Tuesday, July 2, at the “Dog Pound” (the Lawrence family’s private training facility in Florida). Later the same day, Jett underwent X-ray and MRI scans, and it was determined that he had a torn ulnar collateral ligament, or UCL. [Technical diagnosis: proximal thumb avulsion fracture at the insertion of the UCL, a sprain of that same ligament, and an avulsive ligamentous tear of the metacarpophalangeal (MCP) volar plate from its metacarpal attachment.]

Jett is scheduled to undergo a procedure on Thursday, July 4, at the Steadman Clinic in Colorado, after which he will focus on making a return in time for the SuperMotocross opener on September 7 in Concord, North Carolina.

“It’s obviously a bummer, but it’s part of our sport,” Lawrence said. “It was honestly a pretty small crash, but it is what it is. I’ve been pretty lucky with injuries in my career so far, so I guess it’s just my turn. I was happy with the progress we’ve made in the championship since my setback at Hangtown, and I was excited to try and keep my championship. That obviously won’t happen now, but I have a good team around me and will focus on getting healthy again and coming back at 100 percent. I look forward to cheering on Hunter and doing whatever I can to help him the rest of the series.”

Earlier this year, Jett earned the AMA Supercross 450 Championship, which was the seventh professional AMA crown of his young career. Having scored four of five overall wins so far in his AMA Pro Motocross 450 title defense, he currently sits a close second in the points standings to brother and teammate Hunter Lawrence.

“We’re fully behind Jett and will support him through his recovery,” said Lars Lindstrom, Manager for Team Honda HRC. “It’s pretty crazy that three of the championship’s top riders have now been sidelined with the same injury, especially one that’s typically pretty rare. Of course it’s disappointing, but even though Jett has won the last seven championships he’s competed in, he’s still so young and has a lot of success ahead of him. Physically he’s a freak of nature and a specimen, so to keep it that way, allowing him to heal to 100 percent is the goal. With Hunter currently leading the points chase, I like our chances of keeping the AMA Pro Motocross 450 Championship with Honda, and we look forward to working on that this weekend at RedBud. In the meantime, everyone on the team and at Honda sends their love Jett’s way; we’ll miss having him on the line!”

Update: Thursday, July 4, at 09:24 p.m. Eastern

Lawrence posted the following video on his Instagram page, saying surgery "went well."