PITTSBURGH (AP) — T.J. Watt is a quick study. Growing up in a household with two older brothers, he didn't really have a choice. Adapt or get left behind. Quickly.

Those childhood habits die hard for the Pittsburgh Steelers rookie linebacker. His mother Connie taught her boys about organization. Older brother Derek espoused the virtue of cramming spiral notebooks with information during their days together at Wisconsin, a habit T.J. embraced, one that helped fuel the transition from reserve college tight end to NFL starter on the other side of the ball in a span of three years.

"(Derek) said 'I write everything down,'" T.J. Watt said. "Coaches were always like, 'Man, your brother is taking a bunch of notes.' So I take notes every day."

That's not the only writing Watt does. Before he began his first season with the Steelers, he jotted down a list of goals. Some of them were small. One of them was not: be out there with the ones when Pittsburgh opened the season on Sept. 10 in Cleveland.

Done.

When Watt's No. 90 runs out of the tunnel on Sunday against the Browns, he'll be the first rookie outside linebacker to start in an opener for the Steelers since Aaron Jones in 1988. Five-time Pro Bowl teammate James Harrison didn't do it. Neither did Joey Porter, now Watt's position coach. Lamar Woodley and Jason Gildon, too.

Watt had the job from the moment Pittsburgh grabbed him with the 30th overall pick in the draft. "Day zero" as coach Mike Tomlin called it. Yet Tomlin never passed that information along to Watt, who probably would have ignored it anyway.

"I just came out here every day, working my butt off," Watt said. "Just doing whatever they ask me to do."

One thing they're not asking Watt to do? Become a smaller version of oldest brother J.J. Different positions. Different expectations. And far different personalities.

J.J., the three-time NFL Defensive Player of the Year for the Houston Texans, is a 6-foot-5 livewire who's nearly as quick with his mouth as he is with his feet, and is in the middle of a career that could be on its way to the Hall of Fame.

T.J. is ... not that. Oh, he's fast enough. You don't collect sacks on consecutive snaps of your first professional game if you're slow. Yet that's where the similarities end. The youngest of the three Watt brothers in the NFL (Derek plays fullback for the Chargers) is also the quietest.

"He didn't want to come in and do a lot of talking," veteran Steelers linebacker Arthur Moats said. "He just wanted his play to speak for itself. Even in meeting rooms he's quiet. He still is. You could just tell he's always listening, always learning."

It's the path Watt needed to take. He flipped from tight end to linebacker in the middle of his collegiate career, a move that forced him to rethink the way he approaches football. That's where the note taking Derek championed became more than a habit, it became a lifeline.

"I believe if you write it down it's more likely to stick in the memory," Watt said.

Judging by Watt's performance during his first few months on the job, his memory may border on photographic. Porter and inside linebackers coach Jerry Olsavsky keep track of errors during practice and games, everything from missed assignments to missed tackles. The number of times Watt was dinged for a misstep in training camp wasn't just low for a rookie, they were low, period.

"During the pre-snap, he's not flustered," Moats said. "He's ready to play the game."

The proof was immediately apparent to Steelers left tackle Alejandro Villanueva, who spent much of the late spring and summer trying to fend Watt's rapidly expanding repertoire of moves.

"He knows exactly where he's supposed to be," Villanueva said. "He knows exactly what he's supposed to do and when the ball is snapped he doesn't think there's anything preventing him from making the play. When you have that approach as a defensive player, you become more dangerous."

The Steelers need Watt and fellow outside linebacker Bud Dupree to be dangerous to help them return to the playoffs for a fourth consecutive season. It's one of the reasons Tomlin made Watt a starter from the jump, so Watt and Dupree could develop a level of comfort together. The first real test awaits against the Browns, and Watt will find himself lined up opposite perennial Pro Bowl left tackle Joe Thomas.

Watt is looking forward to the challenge, though don't expect him to start texting J.J. for a cheat sheet. For one, J.J. is busy getting the Texans ready for their own opener while raising tens of millions of dollars for Hurricane Harvey relief. For another, this Watt is eager to forge his own identity.

"I'm a professional now," he said. "At the end of the day, I can't always rely on my brother and I never really have."

NOTES: Backup T Jerald Hawkins (knee) was limited in practice. ... S Mike Mitchell, slowed by a lower-body injury during the preseason, was a full participant.

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