PHILADELPHIA -- Eagles defensive coordinator Jim Schwartz didn't rave this weekend about his rookie pass rusher's eye-catching debut.

The rookie pass rusher never boasted about it, either.

That's just what Eagles and coaches have come to expect out of Derek Barnett. The Birds' first-round pick (14th overall) from April sacked Packers quarterbacks twice in Thursday's preseason opener and bursted into the backfield on several occasions, but after Sunday's practice, he told reporters he has specific aspects of his game to shore up.

Barnett shrugged it off the standout performance in his first professional exhibition.

"It's a good start," Barnett said Sunday.

The understated reaction fits with Barnett's personality. Tennessee's all-time sacks leader, Barnett is soft-spoken, and former coaches have described him as somewhat of a film junkie.

He said he just wants to figure out how to improve. And he's going to have to do so if he wants to reach his potential, according to Schwartz.

"There's some things he could do better," Schwartz said when assessing Barnett's performance against the Packers. "He had a couple sort of wasted rushes, where we got out of sync with our front four. Sort of what you expect from a rookie as you start."

Despite the critiques, it's indisputable that Barnett was one of the most dominant players in the game at Green Bay. And the measured responses from Schwartz and Barnett indicate a few things.

First off, it was a preseason game and many starters were on the sidelines when Barnett shined on the field. Secondly, Barnett still needs to develop a wider arsenal of pass-rushing moves if he wants to compete for a starting job on the Eagles or wreck havoc as part of a defensive end rotation.

The rookie's first sack came after he beat Packers offensive tackle Jason Spriggs with and strong inside move, but Barnett knows that maneuver won't work every play.

"It was good to get the first sack on a counter move," Barnett said. "But like I said, I'm still continuing to make sure my rushes aren't the same and getting off quick, so I'm closing that space between me and the tackle as quick as possible."

In other words, there's more work to do.

And perhaps the most significant reason Schwartz and Barnett downplayed the 6-foot-3, 259-pound defensive end's stellar play in Week 1 of the preseason is this: The Eagles don't expect -- and can't afford -- their first-round selection to settle into a rhythm as a mediocre pass rusher. He might be playing with the second-team now, but Barnett will be a key competent Philadelphia's defense in the years to come.

Defensive end Marcus Smith, the 26th overall pick in 2014, flamed out after three years in Philly. If Barnett follows that trends, the Eagles will have a hard time thriving in a defensive system predicated on a fearsome pass rush from the front four.

The Eagles are invested in Barnett, and his play Thursday was just one small step toward proving he can become the type of top-tier player Smith wasn't.

"Obviously, two sacks in a limited number of reps, that's the type of production you expect from a first-round pick," Schwartz said.

Barnett echoed that sentiment. He doesn't want to succumb to Smith's fate or accept a reduced role, so he sees no reason to bound around the locker room and bask in a couple of sacks.

"It's expected of me," Barnett said. "It's not a surprise to me. I'm a first-round pick. I got to come in and help early. That's the way I'm trying to view it."

-- @AaronKazreports