GREEN BAY - Having been given the task of both evaluating and developing rookie running backs, Green Bay Packers assistant coach Ben Sirmans has tried to keep things simple.

There’s a lot of instruction he has to give them, particularly when it comes to pass blocking and releasing out of the backfield. But when it comes to running the ball, he doesn’t have a lot to say.

“You’ve got to be very careful with what you say to running backs, because you want them to react instinctively as opposed to thinking,” Sirmans said. “If they start thinking, as a coach once told me, ‘If you think, you stink.’

“You want to make sure that you don’t affect their instincts through telling them, ‘To be successful in this league, here’s what you have to in this given situation.’ I always tell them, whatever decision you make, we’re going to live with it because playing the position, you have to be able to react to what’s in front of you.”

RELATED:Murphy first up at right tackle after Bulaga injures ankle

ANALYSIS: Packers still waiting for signs Spriggs pick will pay off

Fourth-round pick Jamaal Williams might have a lead over sixth-round pick Aaron Jones, seventh-round pick Devante Mays and undrafted free agents Kalif Phillips and William Stanback, but it isn’t by much.

Together, the backs have 31 carries for 74 yards, an anemic 2.38 yards per carry.

Coach Mike McCarthy would like to get them all more carries, but part of training backs in the Packers' system is teaching them how to pass block. So McCarthy won’t call run after run just to see them in live action.

“The reality of it is, the real challenge of being a three-down player is the pass protection and all the little things,” McCarthy said. “Just being very conscientious of not only rolling them in there with the play time but who they’re playing with, what exactly is the play selection for them.

“Just trying to create as much balance as you can, not only just for an evaluation but for the opportunity for those guys to grow.”

McCarthy and Sirmans also have to see starter Ty Montgomery in action. He has three carries for zero yards with a lost fumble. He missed last week with a leg injury but is expected to play in Denver on Saturday night.

If practice is any indication, Williams will be first off the bench and probably will get some more opportunities with the No. 1 offensive line.

RELATED: Build your own Packers roster

Two for one: Fullback Joe Kerridge was an early star of training camp with his vicious blocks in the half-line drill and his surprising one-handed catch against a linebacker in one-on-ones.

Three weeks later, Kerridge remains firmly in the discussion for a roster spot.

“I think he’s making a pretty good argument,” Sirmans said. “He’s been productive. You can see that he’s gotten better from last year because now he knows and understands the offense.”

On Wednesday, Kerridge and fellow fullback Aaron Ripkowski both took reps with the starting offense during team drills. Kerridge even carried the ball on a running play up the middle, similar to what Ripkowski did quite often last year.

“He’s tough,” Sirmans said of Kerridge. “He’s one of those guys who will play through pain. He understands what the defense is doing and, from what I understand, he’s doing well on special teams. So, he’s making a pretty good argument.”

Feeling the rush: One of the players who has benefited from third-round defensive tackle Montravius Adams being sidelined with a foot injury is Christian Ringo.

With Adams out, Ringo has gotten a considerable amount of snaps in practice and in games and the pass-rush ability he showed at Louisiana-Lafayette has started to surface.

He had two quarterback knockdowns to go along with one tackle in 37 snaps against Washington on Saturday night. In the one-on-one pass-rush drill in practice Wednesday, Ringo beat veteran guard Jahri Evans off the snap and snuck around him for what would have been a pressure or sack.

“Ringo’s had some great rushes,” nose tackle Kenny Clark said.

Ringo, a sixth-round pick in ’15, said the area where he has made the most improvement is with his hands. In college, he was able to beat linemen with quickness, but in the NFL that’s not enough.

“Definitely hands,” Ringo said. “Coach Trgo (Mike Trgovac) has been on me about that since I got here. That’s something I’ve worked on a lot. I’m working on making the next jump.”

Roster extension: This is the first year teams have not had to cut their rosters down to 75 before the final exhibition game.

Rosters can remain at 90 until Sept. 2 when all 32 teams have to be down to 53 players.

McCarthy said he’s 100 percent behind the decision to eliminate the 75 cut.

“From my perspective, the opportunity to coach players a week longer is what you’re looking for,” he said. “I go back to the Super Bowl year, it took 77 players to win that Super Bowl. You don’t win in this league with 53 players.

“The opportunity to continue coaching players a week longer is a benefit for everybody. It’s a benefit for the player, it’s a benefit for the club, it’s definitely makes your team better.”