In the traditional sense of the ground game, there's a clear distinction between the types of players who play tailback and fullback.

But in the Packers' new zone-blocking run scheme, the distinction is blurred in that the fullback isn't necessarily the prototype battering ram fairly customary at the position.

In this scheme, the fullback is more of a backup tailback with the athleticism to carry out the responsibilities of both positions, except he'll rarely carry the ball. It may be easier to find players who fit that description than the straight-ahead blaster of a fullback, but it's not easy to find someone who can excel in the role.

"You have to be an athletic guy, you have to be able to read and adjust like a halfback would," running backs coach Edgar Bennett said. "You have to be a good receiver, you have to be smart so you can pick up your protections. You have to be an overall football player. I think that's the bottom line."

The reason the fullback doesn't need to be a big, bruising blocker is the way the zone scheme works. As the offensive line flows in one direction, with each lineman responsible for an area rather than an individual defender, it's harder for a linebacker to simply pick a hole and attack. So when the fullback is making the read on the defender he needs to block, that player isn't likely to have a full head of steam.

"He's assigned a specific guy, but he's got all those linemen in front of him, knowing their respective gaps, so he doesn't have linebackers running downhill on him all the time," offensive coordinator Jeff Jagodzinski said. "You don't have to be that big hammer to be a fullback in this system."

Jagodzinski brought the zone-blocking scheme here from Atlanta, where he learned it from former offensive line coach Alex Gibbs. The past few years, Justin Griffith has been the starting fullback for the Falcons. Listed at 5-foot-11 and 232 pounds (on a good day, Jagodzinski said), Griffith has more of a tailback's body.

The Broncos, with whom Gibbs first installed the zone-blocking scheme, are another team that doesn't employ a traditional fullback.

"You look at Denver right now, they've got three free agents at fullback, and they were all halfbacks in college," Jagodzinski said. "They were good runners but they weren't quite fast enough."

So where does that leave the Packers in their effort to fill this role, particularly with starter William Henderson out three weeks, and maybe more, with a knee injury? With plenty to work with, actually.

Tailbacks Noah Herron and Samkon Gado as well as the backup tight ends have been "cross-training," as Head Coach Mike McCarthy terms it, taking certain snaps at fullback with Henderson out, along with backup fullback Vonta Leach.

Herron's versatility was noticed during mini-camps and organized team activities (OTAs) in the spring, and his value in that regard has been evident during training camp.

McCarthy already has stated an interest in possibly keeping four tailbacks on the roster, and the ability to help the offense another way certainly bodes well for any of the backs fighting for roster spots.

"In this offense, you're always preparing to play both positions," Bennett said. "If you're a halfback or fullback, you ought to be able to jump in there and play the other position.

"I think all of these guys are more than capable of doing that. I think they have the right attitude to get in there and cover somebody up and make those blocks as a fullback."

Henderson himself has been more of a traditional fullback his first 11 seasons, but the coaching staff believes he can make the adjustment very well because of his experience.

Henderson is still adept at catching passes out of the backfield and has the savvy to handle the role, even though his 6-1, 252-pound frame is larger than a guy like Griffith. So there's every indication Henderson will be the Packers' first option at fullback when he's healthy, which could be as soon as the season opener Sept. 10.

"According to coach, this could add some life to my career because I'm not doing the smash-mouth iso-blocking that I've done in the past," Henderson said. "Not as much anyway. There will be some.

"But the ability for me to get open and wiggle and get around blocks and adjust to different defensive formations is key, it's something I can do."

Ultimately, a traditional fullback may not have a position to call his own in this offense. But that may make for a more well-rounded roster in the end.

"What that does is give you an extra roster spot if a guy can play two positions," Jagodzinski said. "Our tight ends can play fullback, too. David Martin could do it, with what we're asking our fullback to do."

As the preseason continues, the team will continue to explore that option as well.

"It gives you a lot of flexibility to go from a two-back team to a one-back team, but keep all your two-back principles when you have a tight end who can do the fullback responsibilities," McCarthy said.