PHILADELPHIA (973espn.com) - There isn't a ton of uncertainty for the Philadelphia Eagles heading into the 2019 season but linebacker is a position in flux after the organization lost Jordan Hicks in free agency to Arizona.

In the modern NFL, there are only two three-down LBs and that's been Hicks (when healthy) and Nigel Bradham for Jim Schwartz.

The key question is who replaces Hicks in nickel looks and there are plenty of options, starting with two movement-based pass coverage players in Kamu Grugier-Hill and Nate Gerry, bulked-up LBs who started on the back end in college. Zach Brown, the veteran former Pro Bowl selection who signed after his released in Washington, figures to be a two-down player and start in the base defense, be it in the middle or on the weak side.

ONE CONSTANT

During the spring Bradham was out as he continued rehab from offseason surgery so Gerry started at MIKE, alongside Grugier-Hill in the nickel. Plenty of others got first-team reps, however, including free-agent signing L.J. Fort, Brown and even Paul Worrilow, who was limited as he continues rehab from a torn ACL, in the base defense.

If there is going to be a true competition on a deep Eagles team, it's going to be here with Bradham the only proven constant to Schwartz. LB coach Ken Flajole even mentioned T.J. Edwards and Joey Alfieri as two of the best undrafted rookie free agents he's had and said former CFL star Alex Singleton, a very physical player, will show up when the pads come on.

"We know what Nigel Bradham brings to our organization,” Flajole said. “He’s been a very productive guy. He’s filled in for Jordan [Hicks] when Jordan was hurt in the previous two years, so we know Nigel can slip in there [to middle linebacker]. I don’t know if that’s his most natural position but it may be the best thing for our football team. We’ll just have to see.”

PROVEN PRODUCER

Brown is a wild card because he's played at a high-level but not here. At 250 pounds, however, he's an old-school, downhill LB. Lateral movement is not his strength so pass coverage is not his best attribute although Brown understands the position better than anyone on the team and his football smarts should never be underestimated.

“Zach is kind of a late addition, so he’s trying to play catchup a little bit,” Flajole said. “You can tell with him out on the field, he’s played a lot of football and he’s played a lot of good football, so he’s a veteran that gets it. He just needs to get more time in our scheme and he’ll be a good contributor for us.”

THE NEXT STEP

KGH, once a rover at Eastern Illinois, and Gerry, a safety at Nebraska, have made the transition physically and are modern, undersized safeties trained with pass coverage in mind.

With Grugier-Hill the growth has been obvious, starting out as a major contributor on special teams and getting his feet wet as the third LB last season.

“He’s shown a lot of good growth,” Flajole said of Grugier-Hill. “He’s made incremental progress every year that we’ve had him here. I fully expect him to take the next step and be more than just a special teams guy and a spot player on defense. I’d like to think he could be a real factor for us.”

A COACH ON THE FIELD

Gerry, meanwhile, has impressed the coaching staff with a high-level football IQ, opening the door for the MIKE job and the potential to handle the signal calling if he can hold up from a physical standpoint and win the job.

"Nate's never going to be a 250-pound guy but Nate, without a doubt, is probably the brightest guy," Flajole explained. "He's smarter than I am in the meeting room. He gets it. When you've got a back-end perspective, particularly when it comes to the coverage part of it, I think it gives you a unique perspective because all of a sudden, he's the one guy that understands how everything fits together with the back end."

Fort had a big year in coverage last season in Pittsburgh and is going to be a big part of Dave Fipp's special teams but for whatever reason Schwartz started him along slowly in the spring. Perhaps that was just a ramp-up period and he gets the opportunity in training camp.

THE GOAL

Whatever happens, the goal is clear.

"I think everybody is spreading you out and I think when we went through our offseason program and looked at all the tape we were probably in our nickel package about 70 percent of the time," Flajole explained when talking about the role of his pupils in the modern NFL. "Nobody gets in two backs anymore and pounds the ball on you like they used to. ...  We're seeing so much three wides and we are in our nickel package so often that again, all the guys that run well and move well in space, I think it fits their game."

DEPTH CHART:

SAM - Nigel Bradham - The Jim Schwartz favorite is the only constant heading into training camp.

MIKE - Nate Gerry - Coaches rave about Gerry's football IQ. Can he hold up?

WILL - Kamu Grugier-Hill - From special-teamer to spot guy to starter?

WILL/MIKE2 - Zach Brown - If this were 20 years ago Brown would be the Eagles' best LB by a wide margin.

SAM2 - L.J. Fort - The role is there on special teams. Can he earn more?

ON THE BUBBLE:

WILL/MIKE3 - Paul Worrilow - Working his way back from a torn ACL.

WILL/MIKE4 - T.J. Edwards - The Eagles' best UDFA signing

LONGSHOTS:

OLB5 Alex Singleton - CFL star trying to make the leap.

OLB6 Joey Alfieri - Very athletic but raw rookie.

POSITION GRADE: 5.0 [LB is clearly the biggest question mark on the team and the upside is not top-tier by any stretch.}

Eagles Training Camp Preview: The Quarterbacks

Eagles Training Camp Preview: The Running Backs

Eagles Training Camp Preview: The Receivers

Eagles Training Camp Preview: The Tight Ends

Eagles Training Camp Preview: The Offensive Line

Eagles Training Camp Preview: The Defensive Line

-John McMullen covers the Eagles and the NFL for 973espn.com. You can reach him at jmcmullen44@gmail.com or on Twitter @JFMcMullen