Travis Pastrana has been forced to pull out of Sunday's Race of Champions after injuring himself in a Motocross accident in California earlier this week.
The American hurt his knee and hip when he fell and was run over by another rider.
"I was practicing on a Motocross track when I blew out my knee in a corner and was promptly run over by my fat friend Tommy," he said. "Laying in a heap of dust, the first thing I thought was at least I didn't fall off a golf kart!
"A close second was how much I'm going to miss all the crap talking and competitive camaraderie that is unexplainable for anyone who hasn't been a competitor at the Race of Champions.
"I'm bummed that I won't have a chance to race alongside Carl Edwards, I was really looking forward to going for the RoC Nations Cup."
Pastrana is the second driver to pull out of the event through injury following Mark Webber's broken leg two weeks ago. He will be replaced in the Team USA line-up by drift champion Tanner Foust.
Foust, who is also a co-host of Top Gear USA, is excited to be replacing Pastrana to make his Race of Champions debut.
"The investigation will reveal I had nothing to do with Travis' injuries," he joked. "Of course I wish him a speedy recovery and I'm honoured to have this opportunity to represent the USA alongside Carl Edwards on the world stage, racing against guys who are heroes to me."
Pastrana is confident that Foust will be able to do a good job in his place.
"I'm excited that Tanner is the one to take my place," added Pastrana. "Very few drivers can hold a candle to his car control and I think his all round driving background should benefit Team USA."