Arizona Cardinals RB Chris Johnson in line to start

TEMPE, Ariz. - How much does running back Chris Johnson have left? We should begin to find that answer on Sunday when Johnson is expected to start against the Bears in Chicago.

The Cardinals signed Johnson, 29, in training camp because they needed an experienced starting back should Andre Ellington suffer an injury.

Ellington suffered a sprained posterior cruciate ligament in the season opener and is expected to miss one to three weeks.

Johnson, of course, doesn't think he's lost anything, even though he was released by the Titans in 2014 and by the Jets this spring.

"I'm pretty sure I can be pretty dangerous," Johnson this week.

Johnson appreciates the opportunity he's receiving because after being shot in the shoulder in March, he didn't know if any team would be interested.

The Cardinals were. They were looking for a runner similar in style to Ellington, because they didn't want to revamp their blocking schemes.

Ellington and Johnson are smaller backs, whose agility and speed are their best attributes.

But they are different, too. Johnson can effectively run between the tackles, but he's not as good of receiver.

"This isn't a knock on Andre (Ellington) at all because I love Andre and he's a fantastic player," quarterback Carson Palmer said, "but I can't wait to see Chris (Johnson) run the ball. You are just as excited to see Chris Johnson get the ball in his hands as you are Andre."

Rookie David Johnson moves up the depth chart, too, and is an excellent receiver. He proved that in the season opener, taking his only reception 55 yards for a touchdown.

Safety Tyrann Mathieu said he was more intrigued to see "No. 31" (David Johnson) than Chris Johnson.

That's because Mathieu knows what Chris Johnson can do while he's still learning about David Johnson.

"I didn't think he was that fast," Mathieu said, referring to Johnson's touchdown last week. "I knew he was smooth and could catch the ball but I didn't know he had that extra burst. That was pretty encouraging."

SERIES HISTORY: 90th regular-season meeting. Bears lead, 56-27-6, and have won six of the last eight, including the last meeting, in 2012. Both teams had different coaches and management then so there isn't much about that game that is pertinent now. The series dates to 1920 when the Chicago Cardinals played the Decatur Staleys. The Staleys moved to Chicago in 1921 where they became known as the Bears.

INJURY NOTES

--RB Andre Ellington is expected to miss one to three weeks with a sprained knee ligament. Chris Johnson will start and be backed up by Stepfan Taylor and David Johnson.

--OG Mike Iupati practiced this week for the first time since undergoing knee surgery in training camp. He isn't likely to play in Chicago, but he could make his season debut the following week against the 49ers, his old team.