BOURBONNAIS, Ill. -- Despite leading the team in receiving yardage and tying for the Chicago Bears' lead in receptions last season, Johnny Knox finds himself playing second team behind new acquisition Roy Williams.

Bears offensive coordinator Mike Martz shared a few details Wednesday about Knox's mysterious descent down the depth chart.

Martz says inconsistency is to blame even though Knox had 51 catches for 960 yards and five touchdowns in 2010.

"Johnny's very talented," Martz said. "He's very young, and he's still learning how to play. Guys like Johnny have just got to learn to be consistent. The consistency in his play, and that's with all young players really at any position, particularly at that X position, which is kind of that position of the wide receiver.

"So he certainly has the ability. He just is still learning to play and adjust and do the things that we ask him to do."

Knox started 16 games last season in Year 1 of the team operating in Martz's new system and has worked with the coach in the offseason, gaining a significant amount of experience with some of the more intricate nuances of the scheme.

Williams, meanwhile, knows Martz's system from the duo's two years together in Detroit, when the former first-round receiver caught 146 passes for 2,148 yards and 12 touchdowns.

"This is the best offense I've ever been a part of. This is real football here; a lot of conversions, a lot of reading the defense," Williams said. "It's what the NFL is all about."

Still, the team's decision to start off Williams at the No. 1 spot over Knox came as somewhat of a surprise at the beginning of training camp. Knox expressed frustration early on about the demotion but has since changed his tune, choosing instead to focus on winning back his job.

"I was a little bit [surprised], but it's football. I've just got to get out there, compete and try to make plays when my number is called," Knox said. "[Receivers coach Darryl Drake] didn't really tell me anything. He just told me that I needed to get out there and just keep fighting and not to worry. All the little things would play out."

Bears coach Lovie Smith expressed that same sentiment on Monday, and Martz agreed, while also heaping praise on the quality of the team's receivers from the top to the bottom of the roster.

"We'll just let this thing play out. The good thing is we're excited about the receivers we have, the quality," Martz said. "They're all starters, really. So that makes it better. They'll kind of define their roles in the preseason, but [there's a] real good competition going on right now."

The team released its unofficial depth chart Wednesday for the exhibition opener, and Williams was listed as a starter, and Knox a backup.

But even by demonstrating the consistency the staff says he lacks, Knox still may not be able to wrest away the starting job from Williams, who has an extensive background with both Drake -- from their time together at the University of Texas -- and Martz.

"There's still a lot of time left," Knox said. "I know the offense, I'm comfortable with it. I know what I've got to do, and I'll just take it day by day. Everybody's fighting for a job."

Michael C. Wright covers the Bears for ESPNChicago.com and ESPN 1000.