RENTON — Kam Chancellor is making an impression as Seattle's strong safety.

Actually, that impression is more like a dent.

He is the 6-foot-3, 232-pound sledgehammer in the Seahawks' secondary, a player who is big enough to play linebacker in the NFL and so athletic he was recruited to Virginia Tech as a quarterback. In his second year in the NFL, he is making a name for himself with two interceptions and the kind of hits that loosen an opponent's fillings.

"Kam is playing like I hoped he could play," coach Pete Carroll said.

He is Seattle's clean-up hitter, making the kind of plays that make safeties famous.

In the NFL circa 2011, however, those same plays can make you infamous in the league office. Chancellor was fined $20,000 last week for a hit to the head of Baltimore receiver Anquan Boldin, and he may have been billed for his hit on Rams tight end Lance Kendricks on Sunday in St. Louis. Chancellor has heard from the league, but said he wasn't comfortable discussing what fine — if any — he received.

Chancellor's play illustrates the difficulty in policing hits to the head of a defenseless receiver. The rules come from the very admirable goal of preventing head injuries to football players, but they become more difficult when you consider that sometimes a player does everything he can to make a play only to be punished because he failed to avoid hitting the opponent's head.

"It's not as easy as people might think, when you're in a competitive mode," Carroll said. "It's everything you can do to make the play you're supposed to make. You've got to get there as soon as you can and when you're accelerating, you're leaning forward and the first thing that gets there is your helmet.

"That's unfortunate but that's how it goes."

Both Chancellor's penalized hits came on potential receptions, and he did what safeties are taught to do: He separated the receiver from the ball. Against Boldin, Chancellor knocked himself out of the game with a concussion.

There is a difference between vicious — which those hits were — and malicious.

"None of it is intentionally trying to hit a guy in the helmet," Chancellor said.

But that's where Chancellor's strike zone ended up. Each of the opponents was going down.

"Being a tall DB like I am, I was aiming for the guy's chest," Chancellor said. "While he was falling, on his way down, I just turned my head to the side like they asked me to do the previous week. When he fell down, his head just went into my shoulder."

This is the difficulty of using slow-motion to adjudicate a game that is being played at high speed.

So what does Carroll tell his player this week?

"This is what it is, this is the rule," Carroll said. "We have to do everything we can to recognize the situation and to protect yourself and the other guy as well, which means don't try as hard to make the play. That's the problem, you know?"

It would be easier if the only damaging hits were dirty ones. Like a play where the ball has already sailed by the receiver when the safety lowers the boom or the defender lowers his head to hit with the crown of the helmet.

The reality in the NFL isn't always so neatly delineated. That leaves Chancellor caught in the middle. He's playing on a contract he signed as a fifth-round draft pick in 2010, which pays him $450,000 in base salary this season, and he's trying to play both effectively and within the rules.

"I'm just going to do like they asked me to do," Chancellor said. "Protect the middle and just try to play smart."

Notes

• QB Tarvaris Jackson was limited in Wednesday's practice, continuing with the practice regimen in which he throws only during Thursday's practice before starting Sunday.

• WR Sidney Rice (knee), DL Alan Branch (ankle) and WR Ben Obomanu (knee and ankle) did not practice Wednesday, but have not been ruled out for playing this week.

• S Atari Bigby and DL Anthony Hargrove, who both missed Sunday's game because of hamstring injuries, returned to practice Wednesday.

Danny O'Neil: 206-464-2364 or doneil@seattletimes.com. On Twitter @dannyoneil.