That guy is fourth-year man Richard Marshall.
With Lucas gone, Marshall is slated to step up from nickel back and start this season alongside the team's top corner Chris Gamble.
A former second-round pick out of Fresno State in 2006, Marshall spent three seasons behind Lucas and Gamble and has shown enough to warrant a shot at the starting lineup despite struggling down the stretch last season.
But can he handle the job?
Marshall finished last season with 61 tackles, four pass breakups and one interception. He also had two sacks and led the team in special teams tackles with 17. But there were several times last season where Marshall allowed a big pass completion on third down, allowing the opposition to move the chains.
And with Gamble being the closest thing the Panthers have to a "shutdown corner," Marshall will have a bull's-eye on his chest this season.
"I feel like last season wasn't one of my best seasons," Marshall said. "I feel I could have played better, tackled better, just played better on defense and special teams."
Fox, however, denied Marshall's play has slipped.
"Not really," Fox said. "He's a young player. Playing that nickel position is not the world's easiest position. Like all players, you see improvement from one year to the next, and I anticipate that he'll have that kind of improvement this year."
Marshall was part of a secondary that allowed 13 passing touchdowns in the final seven games last season, including two touchdown receptions to Larry Fitzgerald in a devastating 33-13 loss to the Arizona Cardinals in the NFC Divisional Playoffs.
"You can't wait to get back and start working out again and get ready for the season after a game like that," Marshall said of the loss to the Cardinals at home. "(Fitzgerald) made plays and we didn't make the plays we needed to make. He's a good player and made the plays that came to him and they won the game."
Despite hearing rumors that the team might let Lucas go this off-season because of a salary cap figure approaching $8 million, Marshall said he was still surprised when the team made the move.
"For the most part we don't know what is going to happen upstairs," Marshall said. "When it did happen I was a like, 'Wow, they let him go.'"
At that point, the general assumption was Marshall would be the starter.
But Marshall wasn't taking anything for granted.
"I didn't know at that point they were going to bring me into the starting position until we got to minicamp. Then they had me (working with the first team). I had a thought but you don't know for sure until it actually happens," Marshall said.
The Panthers did draft cornerback Sherrod Martin from Troy in the second round, but Fox tends to lean toward players with experience in the league so it's expected Marshall will be given every opportunity to keep the job.
"Everybody wants to start," Marshall said. "Now that I got my chance I just can't let it slip away. I have to capitalize on the chance that was given to me."