ORCHARD PARK, N.Y. (AP) — Bills defensive coordinator Leslie Frazier was in the midst of discussing his ideal prototypical sizes for players at various positions, when Tremaine Edmunds' name was mentioned.

"Hah," Frazier said, before pausing to buy time to put the 20-year-old rookie starting middle linebacker's 6-foot-5, 250-pound frame and sideline-to-sideline range into perspective.

"His height, his size, his speed, that's rare. He's an anomaly in a lot of ways," he said early into training camp last month. "He's unusual in that regard, and we expect him to play up to that."

The Bills are very high on Edmunds. The Virginia Tech product is their second of two first-round selections whom they traded up six spots to draft 16th, and then immediately put him in a starting role during the team's first spring practice.

Easy as Edmunds made the transition from college to the NFL appear during his first few months, Frazier was also cautious in suggesting there might be some bumps ahead once the preseason opens.

A reminder of that came Friday, when Edmunds experienced a few rookie moments in what was a forgettable opening defensive series in Buffalo's 19-17 win at Cleveland.

The worst came on the third snap when Edmunds was caught leaning the wrong way in being fooled by a fake handoff to receiver Antonio Callaway, while running back Carlos Hyde was already heading up the right sideline for a 26-yard gain on a drive that ended with the Browns scoring a touchdown.

On the bright side, Edmunds bounced back by having a hand in three tackles, including one for a 2-yard loss, during his final three defensive series in which the Browns combined for two first downs and gained 31 yards.

"You just don't wake up and then everything is just going to be perfect," Edmunds said, following practice Monday. "It's going to be a process. There's going to be struggles along the way. It's just about how you react to them."

He's focused on getting a shot to bounce back on Sunday, when the Bills host Cincinnati in a game where the starters will get their most extensive playing time of the preseason.

"My head is on just coming out here and getting better. Simple as that," he said.

Coach Sean McDermott said patience is the key in taking into account Edmunds' inexperience.

"We've got to manage expectations," he said. "Certainly, he's done some nice things to this point, but has a long way to go as well, just take it one day, one play at a time."

A former defensive coordinator in Carolina, McDermott mentioned Panthers linebacker Luke Kuechly in noting how familiar he is with dealing with growing pains.

"I saw Luke in his first year, and I can tell you he's a different player now than he was then," McDermott said. "It takes time."

Edmunds is responsible for the play-calling duties and making pre-snap adjustments on a defense looking to build off last season. Though finishing 26th in yards allowed, the Bills were tied for eighth with 25 takeaways, and 18th in points allowed, while going 8-1 when giving up 17 or fewer points.

As a junior last year, Tremaine Edmunds was a Butkus Award finalist as college football's top linebacker after leading Virginia Tech with 109 tackles and 5½ sacks.

Edmunds has a deep NFL tradition in his family.

His father, Ferrell Edmunds, was a two-time Pro Bowl tight end during a seven-year career split between Miami and Seattle.

His oldest brother, Trey Edmunds, is a running back entering his second season with New Orleans.

And his middle brother, safety Terrell Edmunds, was selected by Pittsburgh with the 28th pick in April, making them the first sibling tandem to be chosen in the first round of the same draft.

Veteran linebacker Lorenzo Alexander is struck by the poise Edmunds has shown from his very first practice.

"Very mature. In a day and age when kids or young men come into the league with the expectation of, 'I'm here. I've arrived. Cater to me,'" he said. "He's totally the opposite of that. Very down to earth. Carries himself like a professional."

Alexander saw signs of Edmunds' even-keel maturity on the sideline following the first drive against Cleveland.

"He's carrying a significant weight. I mean, I think there's a lot of expectations after being drafted so high ... he never flustered," Alexander said. "He's going to be fine. He's fine."

NOTES: The Bills said on Monday that rookie QB Josh Allen will start Sunday against the Bengals. ... AJ McCarron , who is still being evaluated for an injury to his throwing shoulder, was spotted at the Bills facility preparing to ride a stationary bike. ... RB LeSean McCoy did not practice because of a sore groin.

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