GREEN BAY – A third-down running back would seemingly have a more specific, narrow job description, but it's actually just the opposite.

Let the quarterback describe it for you.

"You have to do it all," Aaron Rodgers said. "You have to be able to run between the tackles on third-and-medium. On draw plays, you have to be able to pass block, and you have to be able to catch the ball out of the backfield and make people miss. It's a tough job."

Judging by comments from the Packers' coaches this week, mastering all those third-down duties is the last step John Crockett needs to take in order to solidify a place on Green Bay's 53-man roster.

Crockett appeared to take the lead in the race for the No. 3 running back job last week against Oakland, but his work isn't done.

The second preseason game did have its positive developments, though, for the former undrafted North Dakota State star. He had five carries for 27 yards, including a powerful, 10-yard TD run, in the second half after just one rush for minus-1 yard in the first half. He also added four receptions, on four targeted throws, for 27 yards, and might have had more if not for losing his balance on a quick cut after one catch.

"I thought he put his foot down and ran with the authority and the toughness that you saw in spurts last year, and particularly back in his college career," Head Coach Mike McCarthy said.

Those thoughts were echoed by running backs coach Ben Sirmans, who also referenced a play in the second half when QB Joe Callahan was scrambling around, and Crockett managed to get himself open in the flat. He caught the pass and gained 11 yards to move the chains, on third down, no less.

"Those are plays we need to have from guys in his position," Sirmans said, calling it a "smart football play."

The nuances of third-down play get so much attention due to the Packers' desire for all their running backs to be able to play all the downs. In the no-huddle, hurry-up sequences, stopping to substitute a running back on third down would give the defense a chance to substitute for a crucial play.

That's why Crockett's future is not as simple as whether or not he can spell Eddie Lacy or James Starks here or there. If he's needed for extended duty and the Packers want to run the no-huddle, he has to be able to handle it all.

Crockett knows that and all the expectations that come anytime he's in the huddle with Rodgers.

"You have to get on the field with No. 12, and you have to be on the same page," Crockett said. "He's such a meticulous guy, and everything he does is so strategic, you have to have his same mindset when you're out there with him.

"My job is to be on the same page with him, and make plays when plays come my way."

The competition for the No. 3 job behind Lacy and Starks is far from over. Undrafted rookies Brandon Burks from Troy and Brandon Ross from Maryland have both flashed their skills at times, and they'll get plenty of reps in the final two preseason games to state their case as well.

Crockett had a leg up from the beginning, having spent the first 11 games last season on the practice squad before a promotion to the active roster in December. He had a rookie season to absorb the playbook and get accustomed to the special-teams work required of an NFL backup that wasn't his responsibility as a feature back in college.

Special teams are still a work in progress for Crockett, as is his all-around game, but his energies are directed there, not on who might be trying to commandeer his roster spot.

"You don't want to look too deep in that, especially when you're competing, because if you do, that's when you know you've lost the battle," he said. "When you start analyzing other guys and seeing what other guys do, then you're not focusing on your own craft."

And there's plenty to focus on, just on third down alone.

"A lot of stuff happens in a short amount of time at the line of scrimmage, especially on third down," Rodgers said. "The type of blitz packages we'll see from teams throughout the year … you have to be smart, have good preparation, and do some things when you get the ball in your hands."

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