SANTA CLARA (AP) — 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 Tuesday 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 on the 53-man roster since 2011 to be suspended for using a performance-enhancing substance. The others were John Moffitt, Allen Barbre, Winston Guy and Brandon Browner.

A sixth player, cornerback Richard Sherman, had his suspension overturned on appeal.

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.”

Asked Tuesday about Harbaugh’s mention of the Seahawks suspensions, Seattle coach Pete Carroll said: “We’ve kind of dealt with this to set into motion a really clear mindset to take care of business and treat this situation that is around the league very seriously. I don’t know about commenting about anybody else’s team, but as far as we’re concerned we feel like we’ve addressed it directly.”

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.

Quarterback Colin Kaepernick missed three chances from the 5, throwing three straight incomplete passes intended for Michael Crabtree, who got tangled up with a defender on the final play but no holding was called — Harbaugh screamed from the sideline and signaled for a penalty. Kaepernick’s off-balance throw under pressure on fourth down sailed through the end zone.

“We’re definitely looking for a little bit more as far as execution goes,” offensive coordinator Greg Roman said. “There’s a lot of different things we need to improve in, and red zone being one of them, but not at the exclusion of everything else trying to get better at one thing. There’s definitely some extra emphasis. Coach has scripted that in the practices. It’s a careful balance.”

Roman said he soon will sit down for a lengthy meeting with new senior offensive consultant Eric Mangini, who was hired last week.

“In the next week probably we’re going to sit down, just lock ourselves in the room and really look to the future a bit,” Roman said.

Roman is happy to be on the field — and in the meeting room — at all.

He acknowledged he was lucky not to be seriously hurt when a tree fell in a San Jose park where he was on June 1 for some lawn bowling.

“Well, I was standing this way looking this way and my wife was bowling. And then the tree started to fall,” Roman said. “I turned and I saw somebody and I went to take a step to grab them, and then the tree was halfway down. So, I just full sprinted it. I got crushed by it. But, thankfully from my perspective at least, I didn’t take the brunt of the trunk. So, very lucky. Very fortunate.”

He was scratched all over his body.

“I got beat up pretty good. But, can’t keep me down by a tree,” he said. “Natural disasters? No.”