GREEN BAY – For years it was often heard that if any player knew the Packers' offensive playbook as well as quarterback Aaron Rodgers, it was probably fullback John Kuhn.

But now that Kuhn has been gone for more than a year, who's next? Does anyone's familiarity come close?

Strange as it may sound, Don Barclay could be the answer.

The veteran offensive lineman has at least practiced – if not played in a game – at every position up front during his six years with the Packers. And as he appears to be settling into his primary role as backup center for 2017, his playbook knowledge is only growing.

"It lets you control the bus," Barclay said this spring about learning the offense from the center's perspective. "You have to control what's going on out there and make the calls.

"Not only that but it lets you focus in on the whole playbook now. You're really looking at everything. You have to know fronts, you have to know the calls. You can call everything from the right tackle to the left tackle. You're really in control out there, and it feels good."

Barclay would have every right not to feel so good about the upcoming year. After all, he would have been the odds-on-favorite to win the starting right guard job to replace T.J. Lang had 12th-year veteran free agent Jahri Evans not been signed just before the draft.

Instead, Barclay was making all the snaps for the No. 1 offensive line throughout OTAs with starting center Corey Linsley recovering from offseason surgery. He's once again the super-sub, Linsley's top backup as well as possibly the first reserve option at either guard spot given his experience.

It's a role he has not only accepted but owned with pride, and his longtime teammates have nothing but respect for his professionalism, on the field and in the locker room.

"Bringing Don back was a big thing for us," Rodgers said, referring to the re-signing of Barclay this past offseason. "He's really improved his game.

"This is a guy that's started at tackle for us, started at guard for us, and now is in line to be our backup center. That's fantastic, and I give him a lot of credit.  He has a great approach, he's a great teammate, and he continues to show this team how valuable he is to it."

Barclay proved his value early in his career, filling in at right tackle due to injuries as an undrafted rookie from West Virginia in 2012. The following year, he started 14 games at right tackle.

A knee injury in training camp cost him the 2014 season, and he had some rough moments working his way back in 2015, but he got his first NFL start at right guard in 2016 for Lang and would have played more if not for a shoulder injury that cropped up. He then played the final three quarters of the NFC title game in Atlanta at left guard for an injured Lane Taylor.

All that prompted Rodgers to declare prior to the draft and signing of Evans that he didn't think the Packers needed to bring in anyone to replace the departed Lang. Rodgers was comfortable with the pending competition between Barclay, Kyle Murphy and Lucas Patrick, with the QB's comments since then suggesting he pretty much expected Barclay to win the job.

Be that as it may, all Barclay has done in the meantime is earn even more trust from Rodgers as the offseason center, effectively handling the communication duties that come with the position.

"If he can trust me out there to make calls, protect him out there for whatever he needs to do, that's huge," Barclay said. "I just try and fulfill that every day."

While Head Coach Mike McCarthy joked that Barclay's Pittsburgh roots go "a long way around here," his praise for Barclay's versatility and work ethic are genuine.

Offensive line coach James Campen rarely talks about Barclay without making reference to his toughness, both in dealing with difficult situations as a young player and in battling through injuries as a veteran.

"I have all the confidence in the world in Donnie Barclay," Campen said. "Donnie is a pro's pro."

So much so that if Barclay were called upon to fill in at tackle again – 2016 second-round pick Jason Spriggs is probably the first option there now – he'd jump right in without hesitation despite his work of late being focused on the interior spots.

But that's Barclay. Versatility is an overused word as X's and O's change in football these days, but it applies in the old-fashioned way to Barclay.

"It's a good attribute that I have," he said. "Since I've been here, I've always been that guy playing guard, tackle, and now it's center. Anywhere I can fill in.

"I've had a lot of reps all over the place, and I wouldn't be surprised when camp rolls around if I'll be center or guard, both guards. Whatever it is, I'm going to embrace the role."