CHICAGO (CBS) — New Bears wide receiver Roy Williams says offensive coordinator Mike Martz’s system brings the greatest challenge, but also deserves credit for his success.

Calling Martz his “main man,” he said the playing in the NFL should be a challenge, and Martz’s leadership has ensured that it will be.

LISTEN: Roy Williams on the Mully & Hanley Show

“That’s what the NFL is all about. High school is easy, college gets a little difficult, the NFL should be hard,” Williams said. “You hear all the stories, I mean, I went through the West Coast system – it’s OK – and then I went through Jason Garrett’s system – you know, it’s OK, and Mike Martz’s system – you’ve got to have your head on straight at all positions at all times, and it’s tough on us on offense. I know it’s tough for a defense.”

But he pointed out that in one year with Martz while playing for the Detroit Lions in 2006, he had 1,300 yards – the second most in the NFL.

Under Martz, Williams said, “I can just come in and play and be comfortable – I made a couple of mistakes tonight, but that’s part of it.”

Williams also defended Bears quarterback Jay Cutler for sitting out with an injury during the NFC Championship game this past winter, in which the Bears lost to the Green Bay Packers.

“We all should know that if you can play, you’re going to play – especially in a situation like that. When he didn’t play, I knew he has to be hurting,” he said.

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