EAST RUTHERFORD, NJ - DECEMBER 15: Strong safety Antrel Rolle #26 during the 1st half of the Seattle Seahawks 23-0 win over the New York Giants at MetLife Stadium on December 15, 2013 in East Rutherford, New Jersey. (Photo by Ron Antonelli/Getty Images) Antrel Rolle. (Getty Images)

By Dan Durkin—

Editor’s note: This is the fifth piece in a series previewing the 2015 Bears as the first training camp practice approaches July 30. You can find them in one spot here as they’re posted.

(CBS) There’s been anything but safety in numbers when it comes to the last line of the Bears’ defense. Assuming free agent signee Antrel Rolle lines up across from Aaron Rodgers and the potent Packers offense in the Sept. 13 opener, that will be the Bears’ 19th different combination since 2009.

The wheel started spinning since Mike Brown’s departure in 2008 and has yet to come to a stop, despite the team using a selection on a safety in 10 of its last 11 draft classes.

This season, the onus falls on a pair of reunited veterans — Rolle and Ryan Mundy — to be a short-term stop gap as the new regime culls more competition to play a vital role in defensive coordinator Vic Fangio’s scheme, one that demands a high football IQ and being assignment sound while granting freedom to make downhill plays in the run game and opportunistic undercuts in the passing game.

Likely starters:

Free safety: Antrel Rolle (32, 11th year)

Strong safety: Ryan Mundy (30, seventh year)

Other competitors: Sherrod Martin (30, fifth year), Malcolm Bronson (25, first year), Brock Vereen (22, second year), Adrian Amos (22, rookie) and Anthony Jefferson (23, rookie)

Key contributor: Antrel Rolle

Entering his 11th season, Rolle is on the down side of a successful NFL career. He entered the league as a highly coveted cornerback out of Miami, a position he played for the Arizona Cardinals for three seasons before moving to free safety in 2008.

The move to free safety was career-saving for Rolle. Early on at cornerback, he was susceptible to double moves, which led to him giving receivers more cushion and open throwing lanes for quarterbacks to drive the ball into. On the flip side, he was always a physical open-field tackler who never shied away from contact, which are ideal traits for a safety.

Since the position switch, Rolle’s missed only one start in seven seasons, has averaged 74 tackles, snared 19 interceptions, forced eight fumbles and made three Pro Bowl appearances. Last season, he took a step back in run support, but he has experience as the leader of the Giants’ secondary and locker room. Leadership qualities are desperately needed in the Bears’ locker room.

During his visit with the media at the NFL Scouting Combine, Rolle’s former head coach, Tom Coughlin, paid a high compliment to the then-pending free agent.

“I don’t think I was ever involved with a player that was more sincerely interested in how his team could improve,” Coughlin said. “I admire that very much in him as a young man and a leader.”

With the Bears, Rolle will orchestrate the back seven while patrolling center field to make plays on the ball over the deep middle of the field. His presence will be felt by opposing receivers, which is a welcomed change from the recent spate of Bears’ free safeties.

Potential breakthrough player: Adrian Amos

Like Rolle, Amos is a converted cornerback. He spent his first two seasons at Penn State playing on the outside, then transitioned to safety during the 2013 season and stayed there last year.

Amos’ past as a cornerback showed up on film. He has fluid feet and hips to pattern match but was best when driving downhill from his single-high landmark to make plays on the ball. He has free safety skills in a strong safety frame, which suits Fangio’s preference for interchangeability at the position.

Fangio’s known to play big nickel (three-safety) packages, depending on the opponent. The third safety must have coverage skills, so Amos also has an opportunity to earn playing time in that package.

Given the fact he was scouted and identified by the new regime, Amos has an advantage over Brock Vereen. Should something happen to one of the veteran starters, it’s not a stretch to assume Amos may be third in the rotation by the time the regular season arrives.

Also, Amos has a chance to make an immediate impact on special teams.

Final thoughts: Heading into this past offseason, safety was once again a pressing need. General manager Ryan Pace targeted Rolle in free agency, signed Malcolm Bronson the day of the draft after his performance at the team’s mini-camp, drafted Amos and recently signed Sherrod Martin.

Clearly, Pace is looking for a fresh crop of talent at the position, but after the top two (Rolle and Mundy), the group is unproven.

Mundy spent the majority of last season as a box defender lending a hand in run support and led the Bears in tackles. He’s a reliable tackler, smart, an excellent teammate, but he was exposed in coverage.

Injuries forced Vereen onto the field last season, but his performances were mixed at best. His coverage versatility allowed him to play over the slot in a pinch. But as a single-high safety, he played timid over the middle, bypassing chances to make impact collisions when presented, which is a bad sign for his future at the position.

If Rolle can maintain his ironman streak and Mundy (who played in a similar scheme while in Pittsburgh) can provide run support as a box or alley player, the safety position will be in better hands than it has been, but overall, this is an average group that quickly thins out.

Position grade: C-plus.

Dan Durkin covers the Bears for CBSChicago.com and is a frequent contributor to 670 The Score. Follow him on Twitter @djdurkin.