Green Bay Packers center JC Tretter snaps the ball during training camp. Credit: Mark Hoffman

Green Bay – The loss of Don Barclay on Tuesday to a season-ending knee injury reduced the number of offensive linemen that the Green Bay Packers knew could play to four.

Center JC Tretter and tackle Derek Sherrod supplied enough evidence Saturday night in the exhibition opener against the Tennessee Titans in Nashville for the Packers to be optimistic that number actually is six.

In 16 snaps split evenly against starters and backups, Tretter demonstrated an aggressive, hustling approach that was impressive.

Sherrod, in 45 snaps against second- and third-stringers, probably looked better than he ever has since being drafted with the final choice of the first round in 2011.

Surely, the Packers coaching staff wouldn't be ready to anoint either man after their first exposure to full contact. There will be more severe tests ahead, beginning Saturday against the St. Louis Rams and their exceptional defensive line.

But as far as starters go, it couldn't have gone much better for Tretter and Sherrod, and it certainly could have gone much worse. The heavy rainfall made their jobs more difficult, too.

Tretter was matched against nose tackle Sammie Hill, a six-year veteran with four seasons in Detroit and one in St. Louis. He's a better fit in the Titans' new 3-4 defense than he had been in a 4-3.

The Packers were able to control the line of scrimmage in their eight-play (six were carries by James Starks), 64-yard touchdown drive. Tretter was a key reason why.

In a 4-yard run by Starks, Tretter successfully reach-blocked Hill and then tipped Hill over with extra effort. He got good movement against Hill on the next run, then gained double-team help in pancaking defensive tackle Jurrell Casey for an 11-yard rush on third and 3.

When the march ended on Starks' 20-yard burst, Tretter won his one-on-one block against Hill with his persistence, and the nose tackle acted out in frustration as Starks blasted past headed for the end zone.

At 6 feet 3 ½ inches, Tretter is an inch taller than his predecessor, Evan Dietrich-Smith. Having a rangier player in the middle gives the unit a more robust presence.

Later, Tretter turned defensive tackle Karl Klug, an active four-year veteran, on an 11-yard run by DuJuan Harris. He was working his hands, working his technique and carrying the fight to the opposition.

It wasn't all rosy for Tretter. Early on the first drive, Hill pressed Tretter at the line in another one-on-one situation and then came off to make a solo stop of Starks after a 2-yard carry. At 300, Tretter weighs eight to 10 pounds less than Dietrich-Smith, and against someone like the 330-pound Hill there will be occasions when he's overpowered physically.

Count on the Ivy League-educated Tretter to maximize what his body can give. He'll need to be assignment-sure and technically superior to hold up against the behemoths of the interior.

Rookie Corey Linsley followed Tretter and played 28 snaps. Linsley probably had just one, maybe two negative plays. He was adequate.

Still, at this point, there's no competition at center. Tretter clearly is the more athletic and advanced of the two players.

Sherrod took over for David Bakhtiari after the first drive and logged 28 snaps at left tackle and then 17 more at right tackle.

Before Sherrod suffered the horrendous leg injury and subsequent ankle problems that cost him almost two full seasons, he relied on athleticism, wingspan and top-notch feet.

In Nashville, Sherrod didn't seem to be as nimble or as quick as he was at age 22. Back then, he could bench-press 225 pounds only 23 times at the combine. His game was based on finesse.

On the other hand, Sherrod has grown into his body and, at age 25, obviously benefited from extensive weight training and a rebuilt physique. He plays with more power these days, which was evident to a widespread audience for the first time Saturday night.

He actually moved the pile occasionally in the run game. A massive individual (6-5 ½, 320) with incredible 11-inch hands and 35 3/8-inch arms, Sherrod maintained proper angles and consistently walled off defenders from the ball.

At left tackle, Sherrod usually was matched against outside linebacker Akeem Ayers (6-2 ½, 255), a second-round draft choice in 2011. A three-year starter as a 4-3 end, Ayers had six sacks in '12. He was demoted to second team this season.

Ayers tried to take Sherrod around the corner about 10 times but made almost no headway. Late in the first half, Ayers registered a pressure against Sherrod although Scott Tolzien held the ball too long, and then might have earned one-half sack against Sherrod to end the half although guard Andrew Tiller was mostly at fault.

Before that, Sherrod passing off several stunts neatly and never seemed to lose his focus or poise.

At right tackle, Sherrod was even more effective against free agent Brandon Copeland, although his late sloppiness might have been caused by fatigue.

Taking it step by step, Sherrod is on course to becoming a competent player.

First-round review

Now let's take a look at how the Packers' three most recent first-round draft picks fared against the Titans.

Nick Perry played all 26 of his snaps at right outside linebacker. Perry has said his distinct preference is the right side, and with Mike Neal easy to please it has been Neal on the left and Perry on the right with the No. 2 defense most of the summer.

In the opener, Perry wasn't consistent against run or pass. The flashes do remain intriguing and, if he stays healthy, will earn him snaps in base and in customized game-plan packages.

Perry had just four snaps against Michael Roos, a high-caliber starter at left tackle since 2005. His other 22 came against rookie Taylor Lewan, the 11th pick in the draft.

On their fifth snap, Perry detected Lewan sitting back and waiting. Perry got under Lewan's pads and drove him back about five yards before the rookie managed to anchor. Perry also used his muscle against the run, playing through one block by guard Eric Olsen to pile up a carry.

Other times, Lewan (6-7, 309) handled Perry with his size, energy and nastiness. It was a great duel to watch.

The first-round expectations for Perry, the 28th selection in 2012, are old news.

Perry isn't a great player, and almost certainly won't ever be a great player. Nevertheless, he can help the Packers win in a niche role off that right edge.

Datone Jones started at left end in the 3-4 and at left tackle in the 4-2, just as he has since the off-season began.

Jones didn't play the run well as a rookie and, as a result, almost never was used in the base defense. He's still 285, but rigorous weight work and substantial dietary changes have increased his strength.

There were running plays in which Jones was moved by guard Chance Warmack, covered up by right tackle Michael Oher and beat by tight end Craig Stevens. Other times, he would stuff a Titan.

He didn't make any plays in his 20-play stint (12 in the 3-4, eight in four-man fronts). His pass rush was marginal. His effort was high.

For now, Josh Boyd is backing up Mike Daniels at right end and B.J. Raji at nose tackle, at least until nose tackle Letroy Guion returns from a hamstring injury.

Rookie end Khyri Thornton, a third-round pick, took over for Jones late in the first half and finished with 30 snaps. He probably wasn't any better than free agent Luther Robinson, who at least demonstrated some rush. For now, Thornton is a push-type rusher with a limited pass-rush repertoire.

Jones' playing time will be based on his resolve playing the run and his athleticism playing the pass.

Meanwhile, Ha Ha Clinton-Dix made the most of Morgan Burnett's absence (oblique) by playing the entire first half opposite Micah Hyde. His 28-snap breakdown included 16 deep, eight in the box, three in the slot and one low on the weak side against an unbalanced formation.

It was the first live action for Clinton-Dix in a Green Bay uniform. He probably was more impressive in this game than any day in practice.

When Titans coach Ken Whisenhunt decided to have Derek Hagan, an eighth-year wide receiver, block Clinton-Dix on the back side of a running play, the rookie mashed Hagan like he wasn't even there and halted Bishop Sankey after a yard.

When Jackie Battle beat Jamari Lattimore on a check-down, Clinton-Dix came off his downfield coverage and stuck his face in front of the 240-pound fullback to limit the gain to 11.

When Neal blew the sack and Sam Barrington missed the tackle, Clinton-Dix sifted through the wreckage to make a safe, sure tackle of Sankey and prevent a touchdown.

Clinton-Dix's worst play was trying to shoulder tackle diminutive Dexter McCluster without bringing his arms. McCluster kept right on going for an additional five yards.

On the previous play, Clinton-Dix had man coverage near the line on Taylor Thompson. The tight end, a fifth-round draft choice in 2012, appeared to shock the rookie with his speed and found himself wide open down the seam.

Because teams do so little game-planning, it's possible Clinton-Dix had no idea Thompson (6-6, 268) ran 40 yards in 4.56 seconds coming out. The Alabama rookie ran 4.59.

Anyway, Clinton-Dix got on his horse and, as the outstretched Thompson was gathering ball to chest 21 yards downfield, knocked it from his grasp. One way or another, his coverage was a success.

When Burnett returns, the coaches will figure out roles for the safeties in the base and nickel. In the 4-1 defense, the favorites would be Burnett and Clinton-Dix deep and Hyde as the dime back.

Short shorts

■ Jarrett Bush was the best defensive player on the field. In 16 snaps, he had eight tackles (one for loss), a sack and a pressure. "I love him," one scout said. "He seems to be around the ball all the time."

■ Nate Palmer has had a ton of reps all summer, and it continued in the game. Of the last five backups at outside linebacker, he had 23 snaps compared to 13 for Andy Mulumba, eight for Carl Bradford and six apiece for Jayrone Elliott and Adrian Hubbard.

■ B.J. Raji seemed to be lined up offsides on the fumbled exchange between quarterback Jake Locker and center Brian Schwenke.

■ James Starks had a big night running the ball but his performance on special teams wasn't good.