How effective will Justin Smith be on Saturday?

That is the key question facing the 49ers as they prepare for the Packers. If Smith is healthy, the 49ers will have a formidable pass rush and can harass Aaron Rodgers and degrade his passing game. A healthy Justin Smith makes Aldon Smith a better sacker of quarterbacks. If Smith is healthy, the Niners can almost certainly negate the Packers' run game.

But if Smith is not healthy — if he is not Justin Smith — the 49ers' defense is no big deal. Think back to the second half of the Patriots game on Dec. 16 and the Seahawks game on Dec. 23 when Smith could not play because he injured his left triceps.

The 49ers really need Justin Smith to be Justin Smith.

I phoned Santa Rosa resident Gary Furness, a doctor for the California Athletic Commission. Furness specializes in athletic injuries. Before discussing Smith, he wanted me to understand what the triceps does.

"The triceps muscle straightens out the elbow," he said. "Triceps injuries are rare except in weight lifters and football players. A lot of people have no idea what the triceps does. For Smith to be effective he has to be able push off."

Are you following? Smith pushes and pulls at the line of scrimmage. The triceps helps him do that. With a faulty triceps he's not much of a pusher.

Furness discussed two outcomes for Smith depending on the nature of his injury. Remember, the nature of his injury is murky. The Niners never have issued a news release detailing what happened, so there is an area of uncertainty.

The optimistic alternative, a muscle tear:

"Smith would be lucky if he tore a muscle instead of a tendon," Furness said. "If it's a muscle tear it can heal in three to four weeks and it almost never needs operative repair. It's also consistent the 49ers would try to bring him back in a month."

If it's only a muscle tear, what percent of effectiveness could Smith be at on Saturday?

"There's a huge range. I don't know how big the tear is. He could be almost 100 percent, but that is unclear."

Could Smith be a factor in the game?

"Yes, he could be. There would be no effect on his grip strength or leverage. He may really do well."

Will he need surgery after this season?

"Barring another injury, he almost certainly will not need surgery."

One more thing, Smith has been seen wearing a black brace on his left arm. It almost looks like armor. What is the function of the brace?

"With the brace, the force of any collision gets transmitted over a much wider area and is less likely to tear the same spot."

OK, that was the optimistic scenario, the Justin-Smith-is-ready-to-raise-hell scenario.

Here's the not-so-optimistic scenario, a tendon tear. Remember, the Sacramento Bee reported he suffered a partially-torn tendon.

What would a tendon tear mean?

"If the tendon is torn, there's almost a 100 percent need for a surgical procedure and he'd be out for months. You would have to assume he'd be out of the game immediately if he reinjures himself."

Is there a risk of reinjuring himself if he plays with a torn tendon as opposed to a torn muscle?

"If Smith plays with a torn tendon, the risk of worsening the injury goes way up. The biggest risk is tearing the area that was damaged. And it could happen on a routine play as he pushes and pulls."

Why does a tendon not heal as well as a muscle?

"The blood flow to a muscle is among the best in the body. Healing factors are carried quickly to any damaged area. Tendons are different. They are almost &‘a-vascular,' and that means they have almost no blood flow."

As you can see, we are dealing with definitions here — definitions that are partially unknown. If Smith has a muscle boo-boo, he's almost surely ready to go. If it's a tendon owwee, he could be out of the game fast, or he may not even play.

If it's a tendon, heaven help the 49ers.


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.