Villopoto battled with the knee injury throughout his title-winning 2014 Monster Energy Supercross season.
Monster Energy Kawasaki has signed the 2013 Canadian Monster Energy Motocross Nationals Champion Brett Metcalfe to replace Villopoto for the 2014 AMA Pro Motocross season.
“This is definitely not the news I wanted to hear from the doctors,” said Villopoto, who was advised to get his knee operated on as soon as possible.
“We have worked hard to be in position to win championships for Monster Energy Kawasaki and to not be able to race this summer is very disappointing. Going from a really great feeling after winning a fourth straight supercross title, to knowing I am going to spend the summer rehabbing a knee injury is devastating.”
“Obviously this is a big blow for the Monster Energy Kawasaki team,” said Kawasaki Senior Manager of Racing Reid Nordin. “Even with the injury Ryan has shown he is the top rider in our sport, but we are listening to his medical team to make sure he gets his knee fixed properly and he can compete for championships in 2015.”