Carolina Panthers rookie defensive end Julius Peppers was suspended for four games by the NFL on Thursday for violating the league's substance-abuse policy, his agent said.

	Julius Peppers' off-field issues may derail his pursuit of the sacks title and rookie of the year honors.

Agent Marvin Demoff said the league office told him that Peppers had tested positive for a banned substance in a dietary supplement. A source close to Peppers, speaking on condition of anonymity, said Peppers did not test positive for steroids.

Two independent sources told ESPN.com that Peppers tested positive for either ephedrine or a derivative of the stimulant ephedra. The substance, typically absorbed through supplements, is on the league's list of banned substances. The NFL began testing for it this summer.

Demoff said Peppers would appeal the suspension, meaning he can play in Sunday's game against Tampa Bay.

In a statement released together with one from his agent, Peppers said he couldn't discuss the suspension until there's a ruling on his appeal.

"While I would like to provide the fans with more information due to the legal ramifications I cannot comment on the situation and I will not be able to until the appeal process is complete,'' he said.

Peppers practiced with the Panthers (3-6) on Thursday, but did not make himself available to reporters.

The 22-year-old player was an All-American at North Carolina, and after he decided to leave after his junior year, the Panthers kept him in his home state and made him the No. 2 overall pick in the draft. The 6-foot-6, 283-pound player has made an immediate impact, leading the NFL with 10 sacks. He also has one interception.

Peppers can keep playing while his appeal is heard.

"My understanding is, he will be our starting left defensive end this Sunday,'' said coach John Fox. "And all of my focus -- and his, too -- is on the Tampa Bay Buccaneers.''

If the suspension is not overturned, Peppers would begin serving it immediately. Normally, appeals are heard on Tuesdays, the regular day off for NFL players.

Panthers linebacker Mark Fields said the situation did not create a distraction for the team Thursday.

"It's not that serious, so we're not looking at it like it's that serious,'' Fields said. "We're playing Tampa Bay Sunday, and he's playing.''

If Peppers is suspended for all four games, he would lose $235,000 in salary. He signed a seven-year, $62 million contract in July, the richest deal in team history.

If the league suspends him for four games, it would cost him about $235,000 from the seven-year, $62 million contract he signed in July. Peppers is the highest-paid player in Panthers history.

Another Panthers defensive lineman, Brentson Buckner, was hit with a four-game league suspension on Nov. 4 for violating the league's anti-drug policy. George Mavrikes, Buckner's agent, said his client took a dietary substance in training camp to help him lose weight. It contained one of the substances now banned by the league.

Citing confidentiality guidelines, the NFL does not announce the substance for which players test positive, generically only saying that a player violated the substance and steroid abuse policy. But last week Kansas City Chiefs linebacker Lew Bush was suspended, and sources confirmed he tested positive for ephedrine and another banned stimulant, Ma Huang.

The Associated Press and ESPN.com senior writer Len Pasquarelli contributed to this report.