Josh Sitton made a grave mistake Tuesday. He left his cellphone unattended, with no password. This was too easy. T.J. Lang, his usual partner in crime, swiped the phone and fired off a tweet.

Viewer discretion is advised.

"Damn I just took a huge crap.. used a whole roll of t.p. was like mud."

Yes, gross. Sitton couldn't return the favor - Lang's phone has a password. Nothing like a friendly hit-and-run to liven up training camp.

"He was just mad that I got to him before he could get to me," Lang said. "That's all he was mad about. I didn't go overboard. It was pretty harmless."

They're already close friends, what with both pointing a red laser pen at James Jones during one locker room interview. Now comes the hard part for Lang - sticking around and overtaking that left guard spot opposite Sitton. Don't let the pranks fool you. Lang realizes this is a critical camp for him. The third-year veteran figured to be the front-runner at the position heading into camp. Instead, coaches have given first-round pick Derek Sherrod, a tackle since high school, the first crack at the job.

Two weeks in, Sherrod has been erratic while Lang has impressed on the No. 2 offense. This is a sink-or-swim year for the 2009 fourth-round pick. After bouncing around at guard and tackle, this could be Lang's best (and final) shot to earn a long-term spot.

Saturday is his opportunity to build on progress made at practice.

"My No. 1 goal is to get out and compete at the level I've been playing at," Lang said. "I need to keep building on the things I'm doing well. You want to win every block you have out there. This will be a huge evaluation for me, going into the first preseason game.

"I need to go out there, finish and do the extra things to show them I want that spot."

The conventional decision would have been to start Lang immediately at guard, the spot vacated by Daryn Colledge. Instead, the Packers are set on giving Sherrod every opportunity at the position with the No. 1 offense. The rookie has been understandably inconsistent.

Lang knows all about position switches. In two seasons, he has played in 28 games with three starts and some goal-line work on the defensive line sprinkled in. It hasn't always been pretty. In 2009, the Packers allowed an NFL-high 51 sacks.

Cycling back and forth between guard and tackle was "overwhelming" for Lang.

"Looking back, I was frustrated," Lang said. "My first two years, I was a swing guy and had to know multiple positions. You always want to come in, learn one spot and compete for it. Looking back at it now, I think it definitely helped me and my future. If anything happens, teams know I can play both tackle and guard on the left and the right.

"When you're out there as a rookie, you're thinking too much and it slows you down a little bit. When things slow down, your athletic ability can shine."

That's where Lang says he is now. He's comfortable, finally settled into one position. During 11-on-11 segments, he has rarely given any ground to defensive tackles.

B.J. Raji has faced Lang plenty in practice, particularly in one-on-one drills. Raji likes what he's seen in Sherrod, too. He said Sherrod is athletic and maintains good leverage.

With Lang, one quality stands out.

"The big thing with offensive linemen is, you're going to get beat," Raji said. "But he has the ability to recover. That's what separates the good offensive linemen - if a guy beats you with one move and you're able to slide back and get in a good position to keep him off the quarterback. I think T.J. has that ability."

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