A lighter Keenan Allen knows it now.

The old habits had to go.

His early-career diet reads like a county-fair menu: "Everything," Allen said Thursday. "Fried stuff. It was bad."

How he practiced and trained were a work in progress, too. His best game last year, a 121-yard, two-touchdown outburst in November, was followed by comments from teammates that he'd had his best week of practice. Production will fluctuate, reliant on uncontrollable factors. The preparation shouldn't.

That was last season.

Only his second.

"I started to realize how the NFL worked," Allen said. "It may sound cliché or corny or whatever, but (how) you practice (is) how you play, for sure. The work you put in is what you (get) out."

The Chargers wide receiver, 20 years old the day he was drafted, is now 23, a father and a third-year veteran who sounds and — more importantly — looks in training camp like he's finding his stride. Increased maturity and a new wrinkle in the Chargers passing game, featuring more of Allen in the slot, may mean his best is yet to come.

Allen has flashed in camp.

Just Wednesday, he caught a fade route over cornerback Jason Verrett in the end zone. He had two long catches earlier, both with considerable yards after the catch, while motioning and lining up all over the field.

"He's worked hard," coach Mike McCoy said. "It doesn't surprise me one bit with the way he's playing."

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Allen trained with a receivers coach this offseason. He cleaned up his diet, "salad" his one-word answer as to how. His fitness level to begin the spring was far beyond what it was at the same point the past two years.

In 2014, he weighed about 212 pounds.

The Chargers wanted him at 206 for the start of camp. At weigh-ins last week, he stepped on the scale, right at 206.

"I didn't feel tired at all today or yesterday or when we did the conditioning test," Allen said last week. "Just being able to run and not be fatigued, I don't have to think about anything but run and catch the ball. ...

"The growth part is crazy. It's definitely exponential. I feel like I'm so far ahead of where I was when I first came in as far as knowing the game and knowing the concepts of where to be and what we want as an offense."

He has an opportunity to seize.

San Diego signed wide receiver Stevie Johnson in March, days after Eddie Royal left for Chicago via free agency. Royal could play outside; however, it was not where the slot receiver specialized. Johnson is more versatile to that effect.

This enables a new offensive wrinkle.

While Allen has played some slot in San Diego, he figures to see more inside work this year than he has since his college career at California. Allen acknowledged that he's missed the role, calling it "just easier" with the freedom to go two different directions off the line of scrimmage.

The coaching staff, as with other weapons, is devising ways to create opportunities for Johnson and Allen.

"We complement each other for sure," Allen said. "I can play inside. He can play inside. I can play outside. He can play outside. We can be on the same side of the field. That's going to be hard for teams to cover. We know how to get open in a zone. We just kind of play (off of) each other."

"The versatility of Keenan and Stevie, if we get to where they're interchangeable from slot to outside and we can move them around, it's going to be huge for us," quarterback Philip Rivers said. "Keenan's a natural in there. He's an X receiver, but I think he may even tell you that may be his most comfortable spot. If they can be interchangeable, that'd be big."

There is a learning curve to the NFL.

Allen found early success as a rookie, a first shot taken in a battle. Last year, defenses returned fire, scheming and devoting resources to contain him through a myriad of coverages and matchups. Allen faced the likes of Darrelle Revis, Brent Grimes , Richard Sherman and Patrick Peterson at cornerback.

He does not consider 2014 to be a down season. Despite two missed games and only four scores, his 77 receptions still led the team.

But this is the season where he fires back.

"I don't think I'm going to get in the back and forth game of it," Allen said. "I definitely want to be as consistent as possible. Hopefully, I can have a better season than my rookie season — touchdowns, yards, catches, leading everything. That's definitely my goal."