Chris Johnson is the clear-cut No. 1 running back for the Arizona Cardinals thanks to his resurgence this season. But who should fantasy football owners be looking at as an insurance policy in case of injury?

Andre Ellington is the established veteran who has proven to be a solid PPR option when healthy. The only problem is that he can't seem to stay on the field. Since entering the league in 2013, Ellington has missed eight total games, including three this year. Rookie David Johnson appears to be a talented playmaker, as evidenced by his five total touchdowns this year, but it's unclear if the third-rounder is ready to take on a bigger role.

For what it's worth, ESPN Fantasy Football Insider Mike Clay believes Ellington should be on all rosters over D. Johnson in case Arizona loses its starter.

"Andre Ellington played 31 snaps Sunday, which is his highest total since he returned form injury in Week 5," Clay wrote. "Of course, the number is inflated quite a bit because Arizona ran 84 offensive plays against Seattle. Chris Johnson was still the lead back, as he carried the ball on 25 of his 48 snaps. Ellington managed five carries and four targets. Ellington is well ahead of David Johnson (eight snaps) on the depth chart, and is outplaying Chris Johnson this season, but he's simply not seeing enough volume to warrant flex consideration. Ellington should be on your bench, as he'd provide RB2 production in the event of an injury to Chris Johnson."

It's hard for me to agree with Clay's assessment that Ellington has been playing better than Chris Johnson. Obviously, the latter has received considerably more touches, but there's no denying his impressive production. Johnson has four 100-yard games this season and is averaging a rock solid 4.4 yards-per-carry. He ranks second in the NFL in rushing with 734 yards. Ellington has been incredibly productive on a per touch basis (7.6 YPC, 12.1 receiving yards per reception), but those numbers would regress to the mean with a greater workload.

Ellington is the clear choice of David Johnson, but Chris Johnson remains in control of this Arizona backfield and for good reason.