BEREA, Ohio -- The Cleveland Browns have sensed Johnny Manziel's frustration as a backup through seven NFL games because the rookie quarterback is a competitor who's accustomed to producing on the field, coach Mike Pettine said Wednesday.

What else has given Pettine that sense? Manziel is "quiet" around the facility.

"That's a position that can be frustrating," Pettine said. "He's preparing like a starter. It can happen in a span of one play. He has to be ready to go, has to be prepared. There's no reason to believe that he's not."

Manziel, the only first-round quarterback from the rookie class who's not currently playing regularly, has done what's necessary to improve with limited reps in practice and film-room work. But going from a Southeastern Conference star quarterback to "standing there having to watch" is a tough transition, Pettine said.

"The competitor he is is one of the biggest reasons we brought him here," Pettine said. "If he didn't feel [frustrated], I'd be shocked."

Manziel has publicly supported starter Brian Hoyer, who has guided the Browns to a 4-3 record while throwing for eight touchdowns and two interceptions. Manziel said last week he needed to "play my role of backup, and that's that."

Hoyer's current role complicates the Browns' interest in getting a full evaluation on Manziel. In practice, Manziel has shown "flashes" of first-round-level quarterback play, according to Pettine, who admits the Browns won't truly know what they have in the former Heisman Trophy winner without significant snaps on Sundays.

Johnny Manziel has shown signs of frustration from not playing this season, but Browns coach Mike Pettine said he won't force the rookie quarterback into the lineup. AP Photo/Evan Vucci

"That's a question we need to have answered, but it's not something that you can force," Pettine said. "Brian's our starting quarterback. That's a difficult thing to say, 'Let's just go ahead.' All the games are meaningful. If it ever gets to the point where we're potentially up big, down big, or if there's a situation that calls for him to go in, we'll get an opportunity to see him.

"But there's a lot of football left to be played. You're looking for an evaluation at some point, but I don't think you can force it."

The days of elite quarterbacks such as Aaron Rodgers and Steve Young sitting for years are scarcer than ever in today's pressure-cooker NFL. Jacksonville's Blake Bortles, Minnesota's Teddy Bridgewater and Oakland's Derek Carr are all entrenched as full-time rookie starters this year.

Pettine has seen teams make mistakes due to impatience, so his quarterback goals are simple and addressed daily.

"Who gives us best chance to win today? We'll worry about tomorrow down the road," Pettine said.

Pettine also had a good-humored line ready when asked about a Manziel tweet from early Monday morning stating "Legendary night," with Browns running back Terrance West listed on the tweet.

"I don't know if he was still up or whether he was waking up early and getting ready to come into work," Pettine said. "We keep an eye on it. We're not going to micromanage our guys out of the building. We expect them to be mature and handle themselves. If something is a cause for alarm, especially in season, we'll address it."