The San Francisco 49ers are Mike Tyson. Oh, that may be an overstatement. So, let me be more subtle. They show signs of being Mike Tyson, and that should make them worry.

For a time, Tyson was a very good heavyweight. He was the most famous boxer in the world and he knocked out a lot of guys — no one great — just guys. In a list of the all-time great heavyweights I do not include Tyson. In a list of all-time great football teams, I do not include the current 49ers — but they have time to achieve greatness.

How are they like Tyson?

Both are bullies.

Tyson would scare opponents to death and he defeated them before they entered the ring. He couldn't scare Evander Holyfield to death. Holyfield stood up to him and knocked him out, and in the rematch Tyson took the coward's way out and got disqualified for the most famous ear chomp in sports history.

The Niners never bit an ear I know of, but their entire game depends on being bullies.

How are the 49ers bullies?

Their defense, especially their front seven, makes the opponent scared to run the ball — scared to death. The front seven have been the strength of the 49ers, although that strength isn't as strong as it was. How many times have you seen teams give up on the run from the opening play? It's like when Tyson TKO'd petrified Bruce Seldon in the first round. I'm not sure Tyson actually landed a punch. The mere thought of a punch was enough to put Seldon in a swoon.

Because teams were scared to run against the Niners, they reverted to passing, made themselves one dimensional. The Niners' defense could deal with a one-dimensional team that had capitulated on the run. Last season, the 49ers allowed just one back to run for 100 or more yards — in the next-to-last game, in Seattle. Marshawn Lynch ran for 107 yards, did it when Patrick Willis, the 49ers' best run stopper, did not play. That's it — just one 100-yard-plus rusher an entire season. The Niners were dominating.

Things are different this year. The league finally figured out what you do with a bully. You stand up to a bully. If the Niners depend on you to abandon the run, well, you run as hard as you can, just pound them on the ground. You intentionally go against the 49ers' strength and, if you're good and brave and a little lucky, you take their strength away from them and they become like everyone else.

Quick Bill Walsh note — Bill would tell me this all the time. "Lowell, if all you depend on is being tough, you will eventually meet a tougher team. What do you do then?"

I wish Bill could ask Jim Harbaugh this question. Bill always wanted something else in case toughness didn't work. On defense, Harbaugh does not have that something else.

Get this. In the last four games, the 49ers have allowed three backs to rush for more than 100 yards: Ahmad Bradshaw, 116 yards; Lynch, 103, Steven Jackson, 101. On one play on Sunday, Jackson knocked Willis backward. It was awe-inspiring to witness.

We're seeing a trend here: The bully is vulnerable. Next game, the Niners play the Chicago Bears, who have a super runner in Matt Forte. The bully needs to be careful.

The 49ers' problem is more than being an exposed bully. The league now knows the template to defeat — or tie — them. Establish the run early, if you can. Make the Niners have to defend the run. Then they are not as able to defend the pass as easily — especially with corners who have trouble with fast slot receivers like Danny Amendola. Carlos Rogers was so befuddled by Amendola, the coaches had to make a switch to Tarrell Brown.

Here is an exchange I had with Harbaugh at his Monday news conference and tutorial:

Cohn: The Rams really ran well against you yesterday and, with your front seven, I'm not used to seeing that. Why were they able to run so well against you?

Harbaugh: That was especially early. That was a factor early. I thought we did a pretty good job defending the run after that. Give Steven Jackson a lot of credit. He really came to play.

Cohn: Do you feel you still defend the run as well as you did last season?

Harbaugh: Yeah, I think we do a good job defending the run. Not as well in the first quarter of the game, the first couple of series, but for the most part after that, yes.

Without meaning to, Harbaugh was confirming my premise. A team needs to run on the Niners early and get a lead. Then that team also can pass on the Niners. As an extra bonus, the opponent makes the 49ers play catch-up — they have to pass more than they want and run less. That's the way to beat the 49ers.

Am I saying the 49ers are a bad or even an average team? Of course not. They are very good. It's just that a while back Mike Tyson lost his mystique and he never was the same. The 49ers are in danger of losing their mystique. Maybe they lost it already.

For more on the world of sports in general and the Bay Area in particular, go to the Cohn Zohn at cohn.blogs.pressdemocrat.com. You can reach Staff Columnist Lowell Cohn at lowell.cohn@pressdemocrat.com.