GREEN BAY — The Green Bay Packers are using their spring practices as a chance to get their reconfigured offensive line accustomed to their new roles.

Although offseason team activities began Monday, Packers coach Mike McCarthy said Tuesday's practice was the first to feature 11-on-11 work after the first day of practice focused on fundamentals and position drills.

McCarthy made the change last month. The five players — Bryan Bulaga, Josh Sitton, T.J. Lang, Marshall Newhouse and Don Barclay were moved around.

Bulaga was moving from right tackle to left tackle; Sitton and Lang were flip-flopping their spots, with Sitton shifting to left guard and Lang moving to right guard; and Newhouse moving to right tackle, where he'll compete with Barclay and others.

On the first snap of the 11-on-11 sessions, it was Bulaga, Sitton, center Evan Dietrich-Smith, Lang and Newhouse left-to-right in front of quarterback Aaron Rodgers.

But while working together at their new positions was important, individually adjusting both mentally and physically is the biggest challenge, several of the players said.

None of them had been told of the idea beforehand, even though changes were to be expected after Rodgers was sacked a league-high 51 times in 2012 and the Packers' running game ranked 20th in the league in rushing per game (106.4) and 22nd in yards per attempt (3.9).

"It was kind of a quick meeting. Basically, it was, 'This is what's happening: You guys are playing here, you guys are playing here,'" Lang said Tuesday after first learning of the change.

"You're thinking, 'Am I not playing good enough? Am I losing my job?' I don't want to say any of us are secure, because there's always competition."

Discussing the move after practice Tuesday, McCarthy said that the move was made to put the team's best linemen, Bulaga and Sitton, on the left side to protect Rodgers' blind side.

As for how long before the Sept. 8 regular-season opener at San Francisco he'll have his starting five set, McCarthy said he didn't know.

"I'd like to go maybe two years in a row without answering this question about your offensive line," McCarthy said. "Would I like to have five guys ready to say they're our starting five? And play 19 games? That's great. But we have to get them all ready."

Sitton said early on it was a big adjustment.

"I think we're all a little surprised. That's a big move," Sitton said Tuesday. "You don't see a four-position switch on the offensive line very often, so it's definitely surprising, but at the end of the day, it's football. We'll get used to it. We'll continue to grow and hopefully it'll be a good change for us."

According to Lang, McCarthy came down to the offensive line meeting room to explain his reasoning last month. Then, it was time to get to work.

"We all talked about it for 20 minutes, whatever it was, and got a better explanation why it was happening, and it started to make more sense to us," Lang said. "(But) when coach tells you to do something, or asks you to do something, you just have to do it. That's how it works.

"It was definitely awkward for us the first couple days out on the field. Your stance is uncomfortable, your footwork is awful, but we still have a lot of time before we open up the season to make sure we're getting better at our new spots. You just have to keep a positive attitude, go out there and compete every day and just do what you can do to get better."

Bulaga has the added responsibility of protecting the blindside of his team's franchise quarterback.

"It's like a lefty batting right-handed and not being ambidextrous," said Bulaga, who was a left tackle in college at Iowa but has played almost exclusively right tackle since entering the league as the team's first-round pick in 2010.

"You're flipping sides, you're flipping footwork. I think it's a little more physical than mental, just because what we're doing mentally is just flipping calls and flipping plays in our head. That's really all it is. The physical standpoint of footwork, hand placement — everything is turned around a little bit. It takes a little bit of time to get used to that."

Added Lang: "You can't think too much about it; you can't make it bigger than what it is. You just have to keep plugging away every day and stay positive."

That's what Newhouse is trying to do, even though the move is hard to see as anything other than a demotion for him. Newhouse started 13 regular-season games in 2011 after injuries to Bulaga and veteran left tackle Chad Clifton.

When Clifton was released in April 2012, the Packers opted not to move Bulaga to left tackle and stuck with Newhouse on the left side. Newhouse was up and down in 18 starts last season at left tackle.

"You're kind of taken aback," Newhouse said Tuesday. "But I looked inward and acknowledged my role in them having to make the decision (while) also knowing that I can play football and knowing that I had a lot of success at the same time.

"I don't want to be perceived as the weak part of the line. I want to make myself into a strength of the offensive line. It's motivation. I do realize they had to make a decision, and my play was part of them thinking they had to make a decision. So I understand that, I accept that. But I also know I've had a lot of success, so I have to accept the role I've been given and go at it 100 percent. That's all I can really do."

NOTES: Rookie fourth-round pick JC Tretter, an offensive lineman from Cornell, was injured during Monday's practice but McCarthy did not divulge the nature of the injury or give a timetable for his return. The coach said that Tretter would miss the rest of OTAs. ... Defensive end Mike Neal took snaps at outside linebacker during Tuesday's practice. ... Cornerback Sam Shields, who has yet to sign his restricted free-agent tender, was not in attendance. ... Reinstated defensive end Johnny Jolly was not at Tuesday's practice but could return to the team soon. He missed the past three seasons after being suspended by NFL commissioner Roger Goodell, but was reinstated this spring.