If you're a fantasy owner who is always interested in acquiring a running back, an injury to a starter is something that usually gets your attention.

Depending on the NFL team, a backup running back might not be owned in your league. And once you get into Week 6, a starting back on the waiver wire -- let me be Captain Obvious for a second -- receives quite a bit of interest.

With that in mind, I researched the Cardinals' situation when it was announced Monday that Ryan Williams -- who was replacing the oft-injured Beanie Wells -- would miss the rest of the season with a shoulder injury.

What I found was the equivalent of looking for a quality movie and seeing Adam Sandler on every cable channel.

The four Arizona running backs who have recorded carries this season -- Williams, Wells (who is out until at least Week 12 with a toe injury), LaRod Stephens-Howling and William Powell -- have combined for 250 yards on 102 attempts, an average of 2.5 yards per carry. Stephens-Howling and quarterback Kevin Kolb have the Cardinals' only rushing TDs this season (one each).

Only Oakland is averaging fewer than Arizona's 63.4 rushing yards per game.

All of which is why it's been speculated the Cardinals will explore free agents -- Tim Hightower, Joseph Addai, Steve Slaton, Cadillac Williams and Maurice Morris were mentioned in this Arizona Republic blog -- or a trade to fortify their backfield.

Unless they traded for, say, DeAngelo Williams, the Cardinals' options would be free-agent retreads such as Hightower or Addai. Translation: Don't expect much.

If they stay in-house, you probably shouldn't have high hopes, either, but at least there might be a serviceable fantasy choice in Stephens-Howling or Powell.

Of the two, Stephens-Howling would seem to be the best option in fantasy.

In 2010 and '11 with the Cards, Stephens-Howling rushed for a combined 280 yards on 66 carries, a 4.2-yard average, and scored three total touchdowns (one rushing, two receiving). In point-per-reception leagues, he will have the most value -- Stephens-Howling had a combined 29 catches for 345 yards in 2010 and '11.

He has missed the last two games with a hip injury, but is expected to play Sunday against Buffalo.

Powell had a strong preseason in 2012, averaging 5.9 yards per carry and scoring touchdowns in three consecutive games. But he's played in two regular-season games in his career and has all of eight touches (three rushes and five receptions).

The third option being mentioned for the Cardinals at running back is Alfonso Smith, who seems to be the least likely of the trio to have an impact. Smith hasn't had a carry this season, and he averaged 3.4 yards on 30 attempts last season.

If you're desperate and Stephens-Howling seems to be over his hip injury, the latter is at best a flex option this week. As noted in the Arizona Republic blog, Stephens-Howling's 5-foot-7, 185-pound frame probably isn't built for 15 carries or more.

Powell might be worth a roster spot in deep formats, but you shouldn't play him until we have a much better idea how the Cardinals plan to divide the carries -- and if they can manage any semblance of a running game.

An advantage for Stephens-Howling this week: Arizona will play host to Buffalo, which ranks 30th against the run and is allowing an average of 171.8 yards per game on the ground.

The Bills have given up a league-high nine rushing TDs.

We'll be back Tuesday with our weekly waiver-wire picks and break down the Packers' options at running back with Cedric Benson out this week.