"It's a bummer they're gone and I hate to win races like that, but at the same time I've got to focus on each race at a time," Dungey said. "There's a race to be won and that's what the focus has to be on."

Dungey was a star out of the gates in his first season in the 450cc class, becoming the first rookie to sweep the Supercross and motocross titles in 2010.

Last season was the year of Villopoto. After a horrific injury in 2010, he swept both titles last year, along with earning the first $1 million payday in motocross history by capturing the Monster Energy Cup in Las Vegas.

Villopoto kept rolling to start 2012, wrapping up the Supercross title with four races to go, the earliest anyone had clinched the title in the sport's 39-year history, but suffered a knee injury in Seattle that knocked him out of the outdoor season.

Chad Reed also was injured during the Supercross season, setting up what was expected to be a showdown between Dungey and Stewart, two former training partners.

For a while, it lived up to the billing.

Stewart, racing on the outdoor circuit for the first time in three years, opened with two victories ahead of Dungey. But Stewart injured his wrist in the first moto at Thunder Valley in Colorado, and didn't race the second. Dungey won there and the following week at High Point in Pennsylvania, when Stewart, still struggling with a sore wrist, finished fifth in the first moto and again couldn't go in the second.

Stewart is expected to be back this weekend for the Redbud National at RedBud MX Track in Buchanan, Mich., but Dungey has developed a commanding lead -- 54 points ahead of Mike Alessi in second, with Stewart well back in seventh.

"It's easy to get caught up in looking at the whole race season and seeing how you want to do, but what it really comes down to is simplifying things and putting one race at a time and living in the moment," Dungey said. "It's great to be on the podium every weekend, but I just need to let all the preparation I've done take over and do all the talking."

Dungey figured to be on his way to a solid season whether his top competitors were around or not.

After five years riding for Suzuki, Dungey made a somewhat risky move by joining Red Bull KTM, a manufacturer that had struggled to find the consistent success of the big factories such as Yamaha, Suzuki, Honda and Kawasaki.

After an early adjustment period and fighting past a shoulder injury, Dungey started to gel with his new team late in the Supercross season, winning the final two races to finish third in the standings behind Villopoto and Davi Millsaps.

The 22-year-old from Belle Plaine, Minn., has continued his strong ride to start the outdoor season, winning two races while finishing second in the other two.

"It's been a great experience with the new bike, the new team, kind of a whole new atmosphere," Dungey said. "I spent my first five years of my professional career with Suzuki, so the switch was something different, but it's been good."

A new diet has helped.

Feeling sluggish at times over the past year, he went through a series of medical tests to figure out if something was wrong. The tests revealed that he had allergies to milk and eggs, two foods he ate nearly every day.

Since switching to a gluten-free diet, Dungey has noticed a big difference in his energy level.

"When you eat it, your body tries to fight it like it's fighting a cold and you feel a little down," Dungey said. "Overall, getting rid of the stuff I was slightly allergic to I feel better, think clearer, feel stronger in my training, just putting in more productive days."

And there have been a lot of those so far in this motocross season.