Powerful words endure. Eric Kendricks is a 23-year-old who grew up and played college football in California. When describing fellow Vikings linebacker Chad Greenway, Kendricks said:

"What's the quote? He plays like a kid without being childish."

The California kid was quoting a man from another generation, sport and location: legendary Boston Celtics center Bill Russell. "He has the most championships, right?" Kendricks said with a smile.

Not many young athletes can summon a Bill Russell quote with such ease. Kendricks won the Butkus Award as the best linebacker in college football at UCLA last year, and the Vikings drafted him in the second round because of his athletic ability and football intelligence.

But Audie Cole started at middle linebacker in the Vikings' first two preseason games, and Gerald Hodges will get a tryout at the position on Saturday in Dallas.

Despite his accomplishments and maturity, Kendricks has yet to seize the starting job he seemed destined for. He very well could take over in the next two weeks and start in Week 1, but the Vikings' hesitance to promote him immediately is remindful that adaptability is the great unknown for young players.

You can measure a 40-yard dash. You can only guess at how a rookie will assimilate into NFL schemes and NFL life.

Every player the Vikings have taken in the first two rounds of the NFL draft over the past 15 years or so has been physically gifted. Their success has been determined and often limited by their ability to adapt.

You could throw any football concept at Percy Harvin, and he'd grasp it. He also threw fits — and weights — at his coaches.

Randy Moss was similarly shrewd and difficult. Cordarrelle Patterson might have as much talent as Moss and Harvin but has yet to prove he can think the game.

The national consensus was that the Vikings reached when they chose Anthony Barr with the ninth pick in the 2014 draft, because he had played so little at linebacker in his life. Barr became a quick study with a quick first step and ranked as one of the most valuable rookies in the league last year before getting hurt.

Then there's Teddy Bridgewater, who lacked the raw athletic ability of two quarterbacks who went before him in the first round in 2014, but outperformed both because of maturity and savvy.

The Vikings believe they should be a playoff team this year, yet they spent their first two draft picks on players who, unlike Barr, aren't assured of starting jobs in Week 1 of their rookie seasons.

Cornerback Trae Waynes, taken with the 11th pick, has made mistakes in each preseason game and is likely to be a yearlong project rather than an instant contributor.

Kendricks has a better chance to start, but Vikings coach Mike Zimmer leavens his praise of Kendricks with concerns about his anxiousness.

A middle linebacker who is too eager can trap himself in the wash of linemen, or be vulnerable to blocking schemes. Kendricks is learning how to channel his aggressiveness.

He's trying to learn how to play like a kid without being childish.

"I seek out quotes," Kendricks said. "I like anything inspirational. I like to see how it affects me personally."

His brother, Mychal, is another inside linebacker who just signed a four-year contract worth up to $29 million with the Philadelphia Eagles. Between inspirational quotes and real-time advice from his brother, Kendricks does not lack for life advice.

"He always gives me advice," Kendricks said. "He went through everything that I went through before I did. He just tells me to be myself. That's what got me to where I am today. All of the advice other people give me can only get me so far. Being myself is what will get me to where I want to be.

"Right now, the key for me is patience. I have this feeling out there that sometimes everything is moving too fast. I get overeager sometimes."

There's a quote addressing that from the school Kendricks attended. UCLA basketball coach John Wooden used to tell his players, "Be quick, but don't hurry." If Kendricks can adopt that philosophy, he should be a quality NFL player by mid-September.