PITTSBURGH — Two weeks into his NFL career, Pittsburgh Steelers linebacker Ryan Shazier is already well-versed in what’s troubling a defense that hardly looks like its old self.

“Sometimes we take bad angles, sometimes we use the wrong technique for tackles,” the rookie linebacker said. “We’ve got to wrap up and grab cloth instead of trying to use our shoulder and go through people.”

Too often through eight bumpy quarters the Steelers (1-1) have let an opposing running back bounce off them for big plays. Pittsburgh has allowed 340 yards on the ground and an alarming 5.0 yards per carry so far — hardly the return to physical dominance the team promised after an uncharacteristically sloppy 2013. Last season, the defense finished outside the top 10 against the run for the first time in a decade.

Oh, and Cam Newton and the unbeaten Carolina Panthers (2-0) await Sunday night.

“We getting two hands or 1 1/2 and a lot of the guys just aren’t making the tackles we need to make,” Shazier said. “A lot of times we get the guy stood up but don’t get him to the ground. There is a lot of yards after contact. We’ve just got to do the job.”

Something the Steelers struggled to do against Cleveland and Baltimore. The Browns used rookie running backs Isaiah Crowell and Terrance West to key a 24-point second-half comeback in the opener. The Ravens pushed the Steelers at key moments in a 26-6 romp last Thursday night.

Pittsburgh anticipated some adjustment issues following an offseason overhaul that included drafting Shazier and defensive tackle Stephon Tuitt, adding free agent safety Mike Mitchell and nose tackle Cam Thomas. What the Steelers didn’t expect were the same fundamental mistakes that cost them so dearly during an 8-8 season in 2013.

And while it’s far too early to panic, there is cause for concern.

“I think it’s new faces, new guys understanding new techniques, new responsibilities and having habits you’ve had all your football life,” defensive end Brett Keisel said.

“We have to work things out on defense or else we’re going to be up and down like we were last year,” safety Troy Polamalu said.

The roller coaster is already underway. The Steelers aren’t getting gashed so much as they’re letting little plays turn into big ones. They’ve already given up 13 runs of 10 yards or more. On the other 53 rushing attempts they’ve allowed all of 108 yards.

And that’s the frustrating part.

“If you watch the games from the beginning to the end, you can see we’re really stopping the run,” Shazier said. “It’s just that teams have splash plays on us.”

Most of them look like the 41-yard sprint by Baltimore’s Justin Forsett in the fourth quarter that set up Justin Tucker’s fourth field goal. Forsett dashed right, then cut upfield through a gaping hole. Mitchell had Forsett lined up only to whiff as the running back dashed by him.