The juice flows both ways between the Detroit Lions' running backs and assistant head coach and running backs coach Duce Staley.
For Staley, who had three 1,000-yard rushing seasons in 10 years as an NFL running back, juice is something the players are expected to take with them every time they step on the field.
And for the players, the juice is something they quickly came to recognize means a lot to Staley.
Jamaal Williams, signed as a free agent in the offseason after four seasons with the Green Bay Packers, has juice to go with a solid resume as a backup with the Packers.
Staley has seen enough in offseason workouts to think that Williams and D’Andre Swift will give the Lions a strong running-back tandem.
The position could be further strengthened if the Lions sign free agent Todd Gurley, who had three 1,000-yard seasons in his first four years in the NFL but has declined the last two years because of injuries.
Head coach Dan Campbell confirmed Thursday that the Lions are interested in signing Gurley.
"We have interest in Todd," he said. "We're talking. We're talking to his agent.
"That does not affect our feeling and our thoughts on both Swift and Jamaal. We're not going to set a deadline."
Williams welcomed the possibility of Gurley joining the Lions when asked about it Thursday.
"I would love the positive competitiveness in general with all my running back teammates," Williams said.
That answer, and his overall upbeat nature, are part of why Staley has a high regard for Williams.
"It starts with his leadership, on and off the field," Staley said. "Especially in the classroom. He brings that presence, that leadership of a running back who played the game. That's one of the things.
"When you get out on the field, you look at his work ethic. The guy's out there working. He's staying after. He's asking questions. He's catching balls. He's going through footwork.
"It's a pleasure to have him."
And when it's time, Williams brings the juice.
"In our running back room, we talk about juice," Staley said. "We talk about having juice on the field. Any time we go between the lines, things change.
"You're going to have to turn it up a notch. We talk about that. It's natural for him."
None of Staley's comments should be taken as a slight to Swift, or a sign that he's been overlooked. Staley has a long-standing relationship with Swift's family and is high on what he can bring to the Lions.
Swift had a promising rookie season. In 13 games he rushed for 521 yards, 4.6 yards per carry and eight rushing TDs. He added 46 receptions for 357 yards, 7.8 yards per catch and two TDs.
While Swift was showing promise breaking in as an NFL runner, Williams showed his consistency in his fourth year with the Packers with 505 yards rushing. In his previous three seasons, he had rushing seasons of 556, 464 and 460 yards.
Williams appreciates what Staley has said about him. He also thinks that Staley might be reliving – or extending – his playing career through his players.
"Duce is a little more spark-plugged than me, honestly," Williams said. "I think his football side wants to be used.
"In coach mode, all his juice and everything he does, he wants all of that to come out of us."