SANTA CLARA, Calif. >> Jim Harbaugh has used the recent run of suspensions on the division rival Seattle Seahawks for performance-enhancing drug infractions as a reminder to his own San Francisco team: Cheating won’t be tolerated.

Harbaugh’s reigning NFC champion 49ers had begun their three-day minicamp today when the coach was asked about the issue surrounding the Seahawks.

"Is it a concern? I’ve definitely noticed it," Harbaugh said of the Seahawks. "You don’t know what it is. Even when people say what it is, you don’t know that that’s what it is. I’ve heard this thrown out or that, but that’s usually the agents or 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 somebody at their word that I don’t know if you can take them at their word, understanding the circumstances."

Seattle defensive end Bruce Irvin was suspended last month for using a banned substance. A first-round draft pick last year, he will miss the first four games of the regular season — including a Week 2 matchup with the two-time defending NFC West champion Niners in Seattle on Sept. 15. Irvin became the fifth Seahawks player since 2011 to be suspended for using a performance-enhancing substance. The others were John Moffitt, Allen Barbre, Winston Guy and Brandon Browner.

Harbaugh said he has made it clear to his players that he won’t accept breaking the NFL’s policy on performance-enhancing drugs for a perceived edge.

"It has no place in an athlete’s body. Play by the rules," Harbaugh said. "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 in my experience, ever since I was a little kid. We want to be above reproach in everything and do everything by the rules. Because if you don’t, if you cheat to win, then you’ve already lost, according to Bo Schembechler. And (the late Michigan coach) 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."

On the field, the 49ers are spending additional time this offseason on red zone work given their failure to execute on multiple chances in the waning moments of a 34-31 Super Bowl loss to the Baltimore Ravens in New Orleans.