SANTA CLARA — Coach Jim Harbaugh has "definitely noticed" the string of performance-enhancing-drug suspensions that have hit the 49ers' chief division rival, the Seattle Seahawks, over the past 18 months.

"It has no place in an athlete's body," Harbaugh said of performance-enhancing drugs in general. "Play by the rules.

"You always want to be above reproach, especially when you're good, because you don't want people to come back and say, 'They're winning because they're cheating.' That's always going to be a knee-jerk reaction from people I've found in my experience, ever since I was a little kid."

San Francisco 49ers Braylon Edwards, left, is grabbed by Seattle Seahawks Brandon Browner on a touchdown pass attempt in the end zone in first half of
San Francisco 49ers Braylon Edwards, left, is grabbed by Seattle Seahawks Brandon Browner on a touchdown pass attempt in the end zone in first half of their NFL season home opener at Candlestick Park, in San Francisco, Calif., on Sunday, Sept. 11, 2011. The played was ruled defensive pass interference. (Ray Chavez/Staff)

The Seahawks, who finished a half-game behind the 49ers in last season's NFC West standings, have had six players test positive for performance-enhancing substances since December 2011. Only cornerback Richard Sherman escaped a four-game suspension upon appeal.

Harbaugh, speaking at the start of the 49ers' three-day minicamp, did not chastise the Seahawks directly for the officially undisclosed violations.

"You don't know what it is," Harbaugh said of the drugs in question. "Even when people say what it is, you don't know that's what it is. But that's usually the agents of the players themselves saying it's, for example, Adderall.

"But the NFL doesn't release what it actually is. So, you have no idea. You're taking someone at their word, and I don't know you can take them at their word, understanding the circumstances."

Harbaugh said the 49ers have a "constant theme" warning their players about banned substances.

"We want to be above reproach in everything, and do everything be the rules," Harbuagh said. "Because if you cheat, then you've already lost, according to Bo Schembechler. And Bo Schembechler is about next to the word of God as you can get in my mind. It's not the word of God, but it's close."

Sherman recently told ESPN The Magazine that "it does seem that way" whether the Seahawks have a PED problem. He's repeatedly denied taking Adderall.

Last month, defensive end Bruce Irvin became the latest Seahawks players to draw a PED suspension. Others since December 2011 have been handed down to guard John Moffitt, offensive tackle Allen Barbre, safety Winston Guy and safety Brandon Browner.

Linebacker Larry Grant, who played the past two seasons for the 49ers, drew a four-game suspension last month for violating the league's performance-enhancing drug policy. Grant is currently a free agent, and he's issued a statement claiming he did not knowingly take a banned substance.

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