The 25-year-old Washington native only won seven rounds in 2014 SX, but due to multiple podium finishes, Villopoto was able to earn his fourth-straight Supercross title. Only one other rider has completed the feat – the “King of Supercross” Jeremy McGrath.But as the year heads into the outdoor season, Villopoto will not defend his 2013 AMA Pro Motocross Championship title. The KX-F 450 pilot has opted to undergo knee surgery to fix a lingering injury.The injury plagued Villopoto throughout 2014 SX, and his medical team recommended getting surgery as soon as possible. Villopoto concurred, and will be out for 2014 MX.“This is definitely not the news I wanted to hear from the doctors,” said Villopoto. “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.”Substituting for Villopoto on the Monster Energy Kawasaki team will be the 2013 Canadian Monster Energy Pro Motocross Nationals Champion Brett Metcalfe, who will join Jake Weimer in the 450MX class.