Von Miller is a superb pass rusher, a two-time Pro Bowler, the Broncos’ best defensive player and a splitting headache to a team favored to win the Super Bowl.

Miller missed the final training camp session Thursday to plan an appeal strategy with his players union lawyers in Washington, D.C., according to two NFL sources. Meanwhile, the rest of the Broncos were left back at Dove Valley to field questions about his latest transgression.

Miller’s appeal of a four-game suspension for violating the NFL’s drug policy will be heard in some form Tuesday, according to an NFL source. It might be a formal hearing with the NFL version of prosecutor, attorney and clerk recorder. Or it may be an exchange of dialogue.

There are NFL legal matters. And there are county court matters. Miller was arrested Sunday by the Arapahoe County Sheriff’s Department after he tried to buy a gun or gun license. An automatic background check flagged an outstanding warrant on Miller for failing to appear in court. The court appearance Miller missed was for several traffic infractions last October. He was released after his mother posted bond, and he attended the Broncos’ practices Monday, Tuesday and Wednesday before leaving for his meeting Thursday in the nation’s capital.

“Obviously, you’re very disappointed anytime a guy doesn’t take care of his business,” Broncos coach John Fox said. “But we support him. He’s going to be fine. He’s dealt with it. We’ll recover from it.”

Miller was to return to Denver in time to catch the team’s flight Friday to Seattle, where the Broncos will play preseason game No. 2 Saturday night against the Seahawks.

Failure to appear in court over a traffic matter is considered partly no big deal, and partly a concern about Miller’s ability to handle the day-to-day responsibilities of life.

More serious to the Broncos’ ability to win games is his pending four-game suspension.

Miller first tested positive for marijuana during his NFL defensive rookie of the year season of 2011. More recently, the league found Miller in violation of its drug policy and slapped him with a four-game suspension.

The union stated Miller’s case did not involve a performance-enhancing drug (PED), which in turns means he violated the league’s substance-abuse policy.

An NFL source told The Denver Post that the failed test in question was not the result of a sample testing positive for a PED or recreational drug.

However, the league’s drug-testing policy can dock a player with a violation for other reasons — such as missed tests or counseling sessions, an altered test or behavioral issues.

The ruling on Miller’s appeal is expected between Tuesday and Aug. 30, when teams set their 53-man rosters. With Miller gone from practice Thursday, the Broncos inserted Nate Irving into Miller’s strongside linebacker position with pass rusher Shaun Phillips going from No. 1 nickel right defensive end to No. 1 defensive end.

“It’s going to get resolved one way or the other,” Broncos quarterback Peyton Manning said. “We certainly know what we want. But, we are prepared for any possible scenario. That’s how you have to be. If you get all wrapped up into one outcome and it doesn’t end up turning out that way, you don’t really have a Plan B.”

Mike Klis: 303-954-1055, mklis@denverpost.com or twitter.com/mikeklis