Nati Harnik/Associated Press

Two months after head coach Mike Riley retained defensive backs coach Charlton Warren from Bo Pelini's staff, Warren has decided to leave. He's reportedly taking the same role at the University of North Carolina, per Thayer Evans of Sports Illustrated (h/t Hail Varsity).

Riley thought he had finalized his staff in January. With the addition of Keith Williams from Tulane as his wide receivers coach, Riley's Nebraska staff seemed complete. That was until Warren's news broke.

It's not slowing Riley down, though. Instead, the head coach is ready to move forward and find the right person to truly complete his staff.

"We will search for a talented teacher, coach and recruiter to fill the open position on our defensive staff," Riley said, per Mitch Sherman of ESPN.com. "This is a high priority, but we will take the necessary time to find the individual who is the right fit to help lead the young men in the University of Nebraska football program."

Who could that individual be? There are a couple of candidates that Riley should consider when seeking Warren's replacement.

A name that has come up quite a bit already is Eastern Michigan cornerback coach Daniel Bullocks, as the Omaha World-Herald reported. Bullocks played for the Huskers and was a second-round pick in the 2006 NFL draft.

Bullocks has a little experience coaching, too. He began coaching at the University of Northern Iowa in 2012, where he was for three years. He recently (as in January) made the move to Eastern Michigan.

That could easily be the catch for Riley if he was interested in Bullocks. However, a fair pay raise, as well as the opportunity to coach for his alma mater, might just be enough to lure Bullocks away from a brand-new job.

Another potential hire? Riley could take another look at his Oregon State staff and make an offer to secondary coach Rod Perry.

Hiring Perry wouldn't be the worst idea, either. He obviously knows Riley and has worked in defensive coordinator Mark Banker's defense before. It could be an easy transition, especially with the limited time Riley has to find a replacement for Warren.

Perry would bring a good amount of experience to the role, too. According to his bio on OSUBeavers.com, he spent 24 years in the National Football League. That includes three Super Bowls (one as a player for the Rams and the others coaching either the Colts or the Panthers).

Some fans are hesitant for another Oregon State coach to be brought to Nebraska. However, Perry could be the Huskers' guy.

Nebraska fans have thrown out plenty of other suggestions, too. Quite a few of them have Nebraska ties, like Wisconsin's Bill Busch who grew up in O'Neill, Nebraska, and attended Nebraska Wesleyan.

The question is whether Riley wants to hire someone he already knows or make a surprise hire. When it comes to two good options, both Bullocks and Perry would fit the bill.

Could the next defensive backs coach be one of those two? Only time will tell, but Riley doesn't have much of it.