EUGENE — Oregon is installing the “Pistol” into its offense, but just how often will the running back line up directly behind quarterback Justin Herbert?

“I don’t know if I can disclose that,” senior running back Tony Brooks-James said Tuesday. “It is going to be different though.”

The pistol arrived with new running backs coach Jim Mastro, who worked at Nevada from 2004 to 2010 while Wolf Pack head coach Chris Ault created the formation. Oregon head coach Mario Cristobal has some experience with the pistol from his time working at Alabama, and offensive coordinator Marcus Arroyo used it as an assistant at Oklahoma State.

As spring practice comes to an end this week, Oregon sounds like a team ready to rely heavily on a new look in the backfield.

“We want to be majority in it,” Mastro said. “What it does in my opinion is make the defense show their hand a bit, but we will see how it plays out.”

The Ducks may give a hint at just how much they plan to line up in the pistol during Saturday’s spring game.

“It is kind of what we’ve been in during the spring and focused on putting the back into different spots and changing looks up,” Herbert said.

The look itself is not much different for the Ducks, who have relied mostly on one running back alongside the quarterback since the fullback was phased out under Mike Bellotti, Oregon’s head coach from 1995 to 2008. However, Mastro called the execution “drastically different than anything they’ve done in the past.”

Lining up the running back behind the quarterback is intended to make the defense pause.

“The No. 1 thing is that your backfield set doesn’t tip anything,” Mastro explained. “When your back is offset to one side or another, the defense basically sets to where the backfield is.

“In this formation, you can’t do that. You have zone-read football to both sides of the field and the play-action game is much more dynamic. It brings a lot to the table.”

Herbert downplayed how much the pistol would alter Oregon’s offense.

“It is not a major difference,” he said. “I just think we are switching up the looks and doing different things for the defense. We are not changing any of the offense, just putting the backs in different spots and making things look different.”

The Ducks have had running backs line up to the side of the quarterbacks and behind them during practices during the spring, and Cristobal is not hinting at how much Oregon will go with the new formation.

“It is definitely a huge point of emphasis in the spring because it is another aspect, but we are very multiple,” he said. “At times, you might even see us under center now and again. We are a (shotgun), pistol offset back type of operation. We have tempo and sometimes we slow it down. We go fast and the addition of the pistol gives us a couple things that I think are hard to defend. We are trying to continually evolve.”

The biggest difference for the players in the backfield running the pistol is footwork.

“The footwork of the quarterback and running back is everything,” Mastro said. “When you are offset in the (shot)gun there is a lot of leeway for mistakes. In this formation, there is not.”

Herbert returns for his third year as the starter with a couple of senior running backs in Brooks-James and Taj Griffin to go with four freshmen and one sophomore.

“You get used to the footwork and where the back is, so it’s not too different,” Herbert said.

Brooks-James said the timing and vision for running backs are also adjusted a bit.

“It has been different for us, but I can say we got a lot better at it,” he added. “(Mastro) is liking it as well so I assume we are doing something right.”

Mastro spent the past six seasons as running backs coach at Washington State before Cristobal hired him to bring the pistol to Eugene.

“I think it’s bringing in new ideas, we were on the ground floor with it,” Mastro said. “Some ideas they like and some they don’t. I put in my two cents on what I think what would be good or not.”