GREEN BAY, Wis. -

T.J. Lang is a much better blocker than he is a contract negotiator.

When the Green Bay Packers approached their starting left guard and his agent, Mike McCartney, about a contract extension five or six weeks ago, the likeable Lang’s reaction was understandable.

“I was very excited that my name was coming up as a guy that they wanted to re-sign,” Lang said with a wide smile Tuesday afternoon. “I was ready to take the first deal, but of course my agent had to explain some things to me and talk about some structural stuff.”

Once that structural stuff finally was worked out Tuesday, Lang officially signed a four-year, $20.8 million extension that included a $5.5 million guaranteed signing bonus and will keep him in Green Bay through the 2016 season – which is exactly what the 24-year-old wanted as he entered the final year of his rookie contract, even though he might’ve made significantly more on the open market.

“I've never been a money guy,” said Lang, who endured plenty of razzing from his offensive linemates Tuesday – including right guard Josh Sitton, whose extension last year was more lucrative than Lang’s. “Honestly, I was kind of nervous looking through the deal because that's more money than I've ever seen or could ever imagine. Just continue to have my focus on improving as a left guard and as a better teammate – that’s what my focus is on now.”

The Packers, meanwhile, figure to turn their fiscal attention to wide receiver Greg Jennings, whose contract expires after this season, and the triumvirate of linebacker Clay Matthews, defensive lineman B.J. Raji and quarterback Aaron Rodgers. Matthews and Raji are set to become free agents after the 2013 season; Rodgers’ deal expires after 2014 but figures to be redone sooner rather than later.

But Tuesday was about Lang, and just how far he’s come since the Packers took him in the fourth round (No. 109 overall) out of Eastern Michigan in the 2009 NFL Draft. When he arrived, he was a single, 21-year-old rookie with an apartment downtown near all the local watering holes, more money than he ever could have imagined and the cache of being a Packer.

He wasn’t a bad guy. But he was a knucklehead.

“My first year, even a little bit into my second, I don't think I was 100 percent committed to my lifestyle, or my job and my profession. To me at the time, I didn't think it was a problem, but looking back on it now, I'm kind of dumbfounded, how I didn't think that was an issue,” Lang admitted. “I had to really look in the mirror and say, ‘I've got to make a change.’

"I was 21, living downtown, going out three, four nights a week sometimes. I still like to have a little fun now and then, but at the appropriate times – not the night before a practice. But looking back on it, it's like I'm lucky to still be here."

To a man Tuesday, every person who talked about Lang – general manager Ted Thompson, coach Mike McCarthy, offensive line coach James Campen, partner-in-crime Sitton – spoke about how Lang has matured.

“Seeing him grow as a person, grow into a leader, grow into being a solid person …” Campen said. “When he finally decided in the offseason before last year, ‘You know what, it’s not OK for me not to be a starter; I’m a starter,’ he made that transition, and then he worked really hard to get it. I’m proud of him for that part of it.

“He realized, ‘I’ve got to give everything every day, and take my job seriously on and off the field.’ And I think he’s done a very good job of that.”

Off the field, two life experiences last year – the birth of his son, J.J., and the death of his father and namesake, Thomas Lang Sr., from cancer – had profound impacts on him.

"It's just something that kind of made me open up my eyes, I've really got to appreciate the people that care for me and love me," said Lang, who also said his first order of business is to buy his mother a new house. "Because obviously, like my dad, he was gone real quick last year. So I think that's something that hit me, don't forget about those people that have been supporting me my whole life. Take care of them when you get the chance."

And on the field, Lang has focused on his development as a player, going from a versatile backup to invaluable starter after beating out 2011 first-round draft pick Derek Sherrod for the starting left guard gig after Daryn Colledge’s free-agent departure.

“T.J. is a young man who came here (and had) a bumpy start. But he showed a lot of versatility and was able to play multiple positions. Frankly, he could probably play center if we needed to,” McCarthy said. “I’m very, very excited for him. He’s a young man that’s earned it. He’s definitely someone we targeted as one of our core players. With that, I look for T.J. to grow as a person, player and even as a leader on our team.”

Lang’s signing, coupled with Sitton’s extension, the 2010 first-round selection of right tackle Bryan Bulaga and the emergence of third-year left tackle Marshall Newhouse means the Packers have four of their five linemen locked up through 2013. Only veteran Jeff Saturday, whose two-year deal runs through 2013 but doesn’t mean he’ll play next year, is a question mark in front of NFL MVP quarterback Aaron Rodgers.

“I love it, dude. Being able to know we have a group of guys, at least for a while, is a great thing,” Sitton said. “Anytime you play next to the same people, it’s obviously going to help. Everything starts up front, and when we can all be on the same page – it starts with Jeff and Aaron, and goes out – and play next to the same guys, it just builds that chemistry. And being able to have the same guys and build the chemistry off the field helps, also. That helps on the field. I think it’s an awesome thing. I’m super happy for T.J. now, and happy for the whole team. It’s just going to make us better.”

Added first-year offensive coordinator Tom Clements: “You always like to have a solid offensive line that’s played together well. You look at it, we’re young. We’ve got a lot of experience at the center position but everyone else is fairly young with some experience. So that’s a good situation because they can just get better and better.”

And that’s exactly what Lang has done.

“I definitely credit the changes I made both at home and also in here as far as the work ethic, attitude and effort. It's all starting to slowly pay off, so I'm happy about that,” Lang said. “Just cutting out some of the other B.S. that was going on – the drinking and all that crap –once I did that, it showed me, hey, it can change my work ethic in here, how I attack the film room, the weight room, the meetings, and just focus myself 100 percent on getting better. For me, it was pretty easy to do. I understood that if I didn't get a starting spot last year, I might not have a job.

“I think my strongest years are still ahead of me. I'm very excited we got this deal done and give me some security for a couple years to come."