It may seem like a minor thing, and to Jerry Azzinaro it was, but when Fletcher Cox was required to line up directly opposite the tackle rather than over the guard's outside shoulder, he said he let it affect him.

"It probably was the new thing," Cox said of the Eagles' new system on the defensive line. "I've just got to relax. Now I'm relaxed, I'm having a lot of fun."

Cox had his best game of the season on Sunday, according to Eagles coach Chip Kelly and defensive coordinator Bill Davis. The defensive end didn't record a sack or very many tackles, but he hurried Buccaneers quarterback Mike Glennon five times and was constantly around the ball.

"He got more opportunities," said Azzinaro, the Eagles' first-year defensive line coach. "The things that he's been doing all season long were the same things that he did last week."

Cox said there were flashes in the first four games, but that he didn't start showing consistency until the New York Giants game two weeks ago.

"I think I was being too hard on myself and just kind of being uptight and not having a lot of fun," Cox said. "I wouldn't say not having a lot of fun, but I was just being uptight."

When they drafted Cox with the 12th overall pick in 2012, the Eagles touted his ability to play the three-technique 4-3 defensive tackle position (lined up over the guard's outside shoulder) and shoot one gap as a pass rusher.

But with the addition of Kelly and his staff, Cox was moved to defensive end, or more specifically, obligated to play two gaps - meaning both sides of the tackle he was directly opposite - in the 3-4 base defense.

So rather than have responsibility for one gap, Cox and Cedric Thornton, his fellow starter at defensive end, would have to account for two.

"I know what we ask him to do to and I know what 99 percent of NFL guys that play his position do at every snap," Azzinaro said. "There's a guy lined up in front of me. I have to attack that man. I have to beat that man."

To Azzinaro, the 6-foo-4, 300-pound Cox could play in any system.

"When you've got a guy like Fletcher Cox and you look at him from a size standpoint," Azzinaro said, "he fits the bill in any defense."

The Eagles actually play more often in their nickel defense than in their base, which allows Cox to play some three-technique and even some nose tackle, he said, when end Vinny Curry gets his snaps.

"Sometimes we're allowed to play four down [linemen] and that's the fun thing about it," Cox said.

Cox doesn't turn 23 until December. If five games were all it took for him to adapt to a new scheme, the Eagles could have the building block they thought they were getting when they moved up to draft him out of Mississippi State.

"I don't deal with that," Cox said. "I know they brought me here for a reason. They know I can contribute to this team. I just feel like I was being too hard on myself."

Celek and Ertz

Brent Celek was second in receptions on the Eagles from 2009 to '12 - with more catches than DeSean Jackson and LeSean McCoy and only 21 fewer than Jeremy Maclin.

And yet, the tight end is fifth on the team this season with 11 catches. Celek has been productive, averaging 17.8 yards a catch and pulling in two touchdown passes. But he hasn't been a focal point even with Maclin sidelined for the season.

There are several reasons:

The Eagles run the ball more than in years past.

Celek is being asked to stay in and block more often.

Rookie Zach Ertz has cut into some of his snaps.

"Any time they can get him on the field, they want to get him on the field," Celek said of Ertz. "He's a dynamic player. He'll be around for a long time. I really like him and I know they do."

In the first three games, Ertz averaged 16.7 snaps a game. In the last three, he has averaged 35.3. Celek's snaps have dipped marginally, but when the Eagles have two-tight-end personnel, Celek stays in to block (57.6 percent of the time) more often than Ertz (54.3).

Celek had one of his best blocking games Sunday against the Buccaneers. "I love blocking," Celek said. "I honestly don't have a problem with it at all. Any tight end's job is 50-50, usually. The reason I'm happy is I'm doing it better than I've ever done it."

When the Eagles drafted Ertz in the second round after signing James Casey in free agency, there was an assumption that Kelly would lean on his tight ends like other teams have, such as the Patriots. But Eagles quarterbacks have actually thrown less to tight ends than previously.

Ertz is second among tight ends with 10 catches for 163 yards. His opportunities will inevitably increase. Celek, now in his seventh season, admitted in the offseason that the Eagles, in drafting Ertz, were "trying to find somebody to replace me."

He said this week that he wasn't focused on protecting his turf for next season and beyond.

"I'm just going out there trying to do the best that I can do and let it fall where it may and leave the rest up to them," Celek said.

Inside the game

Although DeMeco Ryans remains the de facto leader on defense, a poll of players suggested that the Eagles middle linebacker has more vocal lieutenants than he did last season.

Outside linebacker Connor Barwin and inside linebacker Mychal Kendricks were the two most recognized leaders aside from Ryans. Barwin has integrated himself despite having spent his first four NFL seasons in Houston and Kendricks is no longer a rookie.

"I'm definitely more comfortable with myself being a leader out there on the field," said Kendricks, now in his second season. "We just don't have one leader."

Leadership can be a nebulous term, but the Eagles were sorely lacking in it last season, or lacking in players willing to follow.

"It's just two totally different years," Ryans said. "It's hard for me to compare. This is totally a new group of guys. I feel like we have a younger group of guys."

The Eagles are fourth in the league on third-down conversions at 45.9 percent. But they're the most successful team on third down and 5 (or less), converting 74.4 percent.

They rush from that distance 59 percent of the time. Only the Panthers (60.1 percent) run more, but the Eagles have a greater conversion rate - 78.3 to 70.6 percent - on third and 5 (or less).

Having running back LeSean McCoy certainly helps, but the pace in which the offense runs some of its third down plays seems to also give the Eagles an advantage.

"I don't know whether it's the up-tempo," Kelly said. "Whether we run or pass we're usually in a pretty decent clip in terms of getting the play in. I don't think it's a matchup thing because most people are playing us in nickel anyway."

Coordinator Bill Davis has often employed an umbrella zone to take away vertical passes, but the Eagles have been torched on underneath routes run 0-9 yards off the line of scrimmage.

Opposing quarterbacks have completed 108 of 135 passes (80 percent) for 1,046 yards and seven touchdowns against three interceptions.

Here's the rest of the breakdown by distance:

20-plus yards: 7 of 28 for 228 yards, one TD, one INT.

10-19 yards: 30 of 54 for 519 yards, three TDs, two INTs.

Minus yards: 21 of 22 for 162 yards, two TDs.

Inside the Locker Room

It's unclear if the majority of his carries are designed to run outside, but 23 of Bryce Brown's 33 carries have been off the tackles or around the end. He has gained 57 yards on those tries for a 2.5 average. Brown's gained 38 yards on 10 carries inside the tackles (3.8 average). "I go wherever my vision takes me," Brown said. "I think I'm doing well as far as my reads." . . .

Damaris Johnson fielded the first kickoff against the Bucs 8 yards deep in the end zone and was dropped at the 15-yard line. Kelly said on Monday that the kick was too deep, but Johnson said, given the chance, he would have returned it again. "Normally, it's 5-6 yards deep, but coach has confidence in me and says if I get a low kicked ball, I can field that," Johnson said. . . .

Brandon Boykin, who returned kicks most of last season, is second on the kick-return depth chart. He said not returning has helped him conserve some energy, "but if it was up to me I would still want to return." . . .

Practice-squad tackle Michael Bamiro isn't afraid to admit that he is a project. The 6-8, 340-pound picked up football only four years ago. He said Eagles offensive line coach Jeff Stoutland has taught him the vertical step and, more important, eliminating distractions before he blocks. "I get in the habit of thinking a lot and I overthink situations," said Bamiro, who played at FCS Stony Brook. . . . Bamiro, by the way, has the largest feet on the team - size 18 - along with 6-7 tackle Dennis Kelly. Six-foot-8 defensive end Clifton Geathers wears a size 15.

jmclane@phillynews.com

@Jeff_McLane