The danger of ranking running backs in August was made perfectly clear last Thursday, when we learned Browns rookie Trent Richardson would have knee surgery.

Later that night, the Chargers' Ryan Mathews fractured his clavicle in San Diego's preseason opener and is expected to miss 4 to 6 weeks.

You could say we've made some changes to these rankings.

Some notable updates from the running back rankings we posted Aug. 8 (the above link reflects our current rankings):

-- Chargers coach Norv Turner said Mathews' injury is "not so bad." I can only hope. In a keeper league in which I participate, I traded for Mathews prior to training camp and now must decide if he will still be one of my three keepers (probably).

The Chargers open the season Monday, Sept. 10 at Oakland --  31 days after Mathews' surgery. The guess here is Mathews will return in Week 2 against Tennessee, and considering the lack of studs at the position, I think he remains a top-10 player at the position.

Yes, injuries are a concern -- Mathews has played 26 games in two years. But consider this: Last season, he averaged 4.9 yards per carry and caught 50 passes. In 14 games, he racked up 1,546 total yards.

Would you rather have Mathews coming off a shoulder injury or Adrian Peterson following an ACL tear.

I'll take Mathews.

-- Richardson, who is expected to start the Browns' opener against the Eagles, dropped from No. 14 to 17.

-- The (expected) uncertainty of the backfield situation in Washington -- Mike Shanahan, tormenting fantasy owners since 1995 -- has resulted in Roy Helu dropping from No. 24 to 29 at running back. Redskins teammate Evan Royster, who could be Washington's featured back (your guess is as good as mine when it comes to Shanahan), went from unranked in the top 50 to No. 41. Another Redskin, the (always) beat-up Tim Hightower, dropped from No. 41 to out of the rankings.

-- Ronnie Brown, who would start the season opener for the Chargers if Mathews can't go, is in the top 50 at No. 47. Don't get too excited about Brown, who averaged 3.2 yards per carry in a limited role for the Eagles last season.

This week's batch of waiver-wire candidates is the weakest of the season, so we will present a few reminders before we unveil the highly anticipated top five.

-- Bengals running back Cedric Benson will serve his one-game suspension this week, leaving Bernard Scott as the featured back. Don't expect Scott to have a huge game Sunday at Seattle, which is allowing only 3.2 yards per carry, but if you need a one-game replacement because of bye weeks, Scott is a decent option as a low-end No. 2 back or upper-level flex play.

-- We wrote about DeMarco Murray extensively on Monday, but he entered this week available in more than 64 percent of the leagues on ESPN.com, so he has to be mentioned in this space. Murray is a no-doubt-about-it choice as the top waiver-wire candidate if he's still available in your league.

-- We broke down the value of Seahawks running back Maurice Morris here, and mentioned him again here.

On to this week's waiver-wire selections. A quick reminder: We choose players who are available in more than half of the leagues on ESPN.com (this week's group is available in more than 64 percent of the ESPN formats).

1. Steve Breaston, WR, Chiefs (owned in 35.4 percent of the ESPN leagues): Breaston has 13 receptions for 205 yards and two touchdowns in his last three games, a span in which the Chiefs are 3-0 and averaging 26 points per contest. This week's matchup against the Chargers (No. 3 vs. the pass) isn't great, but Kansas City will face Miami (No. 21 vs. the pass), Denver (No. 19) and New England (No. 32) in Weeks 9, 10 and 11.

2. Demaryius Thomas, WR, Broncos (owned in 2.7 percent of the ESPN leagues): He made his season debut last week at Miami (aka The Game That Gave ESPN Another Reason To Debate Tebow) and had three catches for 27 yards and a TD. Thomas, a first-round pick by the Broncos in 2010, received a team-high 10 targets last week, and the trade of Brandon Lloyd to St. Louis should make Thomas Denver's second-best fantasy option at receiver (behind Eric Decker). I would consider Thomas a No. 4 or 5 receiver in deeper leagues.

3. Delone Carter, RB, Colts (16.9 percent): He is Indy's leading rusher at 259 yards, and last week was the Colts' only bright spot against the Saints (10 carries for 89 yards and a score). With Joseph Addai battling a hamstring injury, Carter -- a rookie fourth-round pick -- has received 36 carries the last three games. Even if Addai is forced to sit this week, Carter likely will share carries with Donald Brown (nine rushes for 47 yards last week), but he seems to have emerged as the Colts' top backfield option. If Addai is out, Carter is a decent flex play Sunday at Tennessee, which ranks 24th against the run.

4. Roy Helu, RB, Redskins (15.3 percent): Mike Shanahan warning! Mike Shanahan warning! As we wrote Monday, who knows what the Redskins will do now that Tim Hightower is out for the season? Ryan Torain would seem to be next in line, but Helu, a rookie fourth-round pick, has value strictly because of the possibility he could earn the featured role at some point this season. Helu has 27 carries for 131 yards this season (4.9), but he has only three rushes for 5 yards in Washington's last two games. I would rather avoid both Torain and Helu until their roles are more clearly defined, but Helu can be a Week 8 desperation play if you base it strictly on the Redskins' matchup (the Bills own the league's third-worst run defense and are giving up 5.1 yards per carry).

5. Heath Miller, TE, Steelers (14.0 percent): Miller has four receptions in each of his last two games, and he has a TD in two of his last three. He caught four passes for 59 yards and a score last week at Arizona, and Sunday the Steelers will play host to the Patriots and their league-worst pass defense (322 yards per game allowed). Miller should be considered a top-10 tight end this week.

Past waiver-wire picks who remain undervalued: DeMarco Murray, RB, Cowboys (owned in 34.6 percent of the ESPN leagues); Bernard Scott, RB, Bengals (4.0 percent); Maurice Morris, RB, Lions (11.9); Greg Little, WR, Browns (9.0); Jerome Simpson, WR, Bengals (33.8); David Nelson, WR, Bills (33.2); Jabar Gaffney, WR, Redskins (6.6); Jermaine Gresham, TE, Bengals (30.6).

According to ESPN.com's ownership percentages, DeMarco Murray is available in more than 64 percent of the fantasy leagues run by the Worldwide Leader.

That number seems way too high, but the stat I'm more curious about is the percentage of owners who left Murray on their bench in Week 7 against the Rams, owners of the league's worst run defense.

Maybe I'm one of the few knuckleheads who did -- in my defense, I started Chris Johnson, Matt Forte and Darren McFadden (my top three draft picks). I watched in horror as McFadden was injured early, Johnson had another unproductive game and Murray ran for a Cowboys franchise-record 253 yards on 25 carries -- in a game he didn't even start.

Murray, Dallas' third-round pick in 2011, missed most of training camp because of a hamstring injury and was getting his chance only because of a high ankle sprain suffered by Felix Jones.

We should also keep in mind that the Rams have been AWFUL against the run (183.8 yards allowed per game and 5.5 yards allowed per carry).

Will Murray deserve to be a fantasy starter the rest of the way? We have no way of knowing.

What we do know is if the Cowboys decide to make him their featured back over Jones once the latter is healthy, it will be an easy decision. Take a look at Dallas' schedule in Weeks 8 through 13: at Philadelphia (No. 23 vs. the run), vs. Seattle (No. 10), vs. Buffalo (No. 30), at Washington (No. 17), vs. Miami (No. 20) and at Arizona (No. 13).

We already are certain Murray is much more valuable than Tashard Choice, who received only two carries as Dallas' starter Sunday. The guess here is he will be a better play than Jones the rest of the way, too.

The problem: If the Cowboys don't agree and go to the dreaded backfield-by-committee plan when Jones returns, Murray will be a No. 3 fantasy back at best.

Take your time getting healthy, Felix. Seriously, take a long time.

Tebow time

I understand why Tim Tebow annoys fans. I get that the experts question his accuracy, his mechanics and whatever else the film shows.

What I don't understand is any skepticism that he's a fantasy starter at quarterback -- assuming, of course, he continues to hold the Broncos' job over Kyle Orton.

As we outlined on Oct. 11, Tebow produces when he plays. Sunday at Miami, he was awful for 54 minutes and 37 seconds (4-for-14 for 40 yards, and the Broncos were 0-for-10 on third down), and great from that point forward.

Tebow finished with 161 yards passing, two touchdowns, eight carries for 65 yards and a two-point conversion. He led Denver to 15 points in the last 2:44 of regulation and an overtime win -- albeit over a winless team.

Again, he produces. He's a top-10 or top-12 fantasy quarterback.

The endless debates, ESPN roundtables and everything else does get to be too much. But that doesn't mean he should be on your bench.

A few more quick takes from Week 7:

-- Until Jahvid Best returns from a concussion (and there is some speculation he won't this season), the Lions appear to have decided on a timeshare between Maurice Morris (nine carries for 50 yards and two catches for 13 yards on Sunday) and Keiland Williams (nine carries for 44 yards). Hint: Stay away.

-- Jackie Battle appears to be the Chiefs' choice as their featured back, though Dexter McCluster and Thomas Jones did receive a combined 19 carries on Sunday. Battle had 16 carries for 76 yards at Oakland, giving him 35 rushes for 195 yards in his last two contests. The presence of McCluster and Jones makes Battle more of a flex play, but he's still a decent option, depending on the matchup (and this week, it's a good one, since the Chargers rank 21st against the run).

-- Mike Shanahan, Fantasy Tormentor, returned to Tim Hightower as his featured back on Sunday, and the latter was productive until he suffered a torn ACL on Sunday. Next up, we can only assume (which is dangerous when Shanahan is involved), in Washington is Ryan Torain, who had 19 carries for 135 yards and a touchdown on Oct. 2 against the (you guessed it) Rams but has received all of 12 attempts since. Don't discount rookie Roy Helu as an option, though, since the 2011 fourth-round pick has averaged 4.9 yards on 27 carries this season.

On second thought, maybe we should all just avoid Washington running backs.

We'll be back Tuesday with waiver-wire picks for Week 8. Until then, enjoy Jon Gruden tonight.

Speak with a Jamaal Charles owner and one of the first things he or she will say to you will have something to do with getting more opportunities.

The electric Chiefs running back rushed for 1,467 yards in 2010, averaging 6.4 yards per carry. He caught 45 passes for 468 yards, giving him an incredible norm of 7.0 yards per touch. Even more ridiculous: Charles had a combined 1,935 rushing and receiving yards, despite getting 17.2 touches per game.

This season, Charles -- a consensus top-five overall choice in fantasy -- didn't make it past Week 2. Sunday, on his second carry of the game, he suffered what ESPN reported shortly after the game was a torn ACL in his left knee.

An MRI later Monday is expected to confirm the report, which would leave many owners scrambling to replace their top running back.

If you're looking to the waiver wire for help this week, there probably won't be much.

The best options, in fact, might be on Charles' team.

Backup Thomas Jones entered the weekend owned in 61.5 percent of the leagues on ESPN. Dexter McCluster, a second-round pick by Kansas City in 2010, was owned in only 7.0 percent of the ESPN formats.

Jones rushed for 896 yards and six touchdowns last season. It marked the first time in six seasons in which he didn't rush for at least 1,119 yards.

In 2008 and '09, Jones gained a combined 2,714 yards on the ground and scored 29 combined rushing and receiving TDs.

At 33, his best days are behind him, but he can still be a useful player in non-point-per-reception leagues.

In PPR leagues, McCluster is a better option than Jones, who had an average of 12 catches per year in 2009 and '10.

McCluster is way too small (5-foot-8, 170 pounds) to get 20-plus carries, but he is explosive (he had eight carries for 51 yards Sunday) and he can get a handful of catches per game (he has nine receptions thus far in 2011).

Neither player should be considered anything more than a fringe No. 3 running back in a 12-team league, but if you've lost Charles, you're probably desperate enough to give one a chance.

Two other long-shot options at running back are a pair of rookies -- the Colts' Delone Carter and the Redskins' Roy Helu.

Carter had 11 carries for 46 yards on Sunday against the Browns, and he has 18 rushing attempts in Indy's first two games -- compared to Joseph Addai's 22. Carter has yet to catch a pass, and Addai is obviously the better fantasy option, but the Copley High School product is the no-doubt-about-it No. 2 back in Indianapolis, ahead of 2009 first-round pick Donald Brown, who has zero carries in two games.

Helu, meanwhile, had 10 rushes for 74 yards and three receptions for 38 yards Sunday against the Cardinals. Tim Hightower is the featured back in Washington, as his 168 rushing yards in two games attest, but Helu can be productive in games in which the Redskins have the lead and long-time fantasy tormentor Mike Shanahan is able to spread the carries around.

Of the four options we've discussed here, McCluster is the best in PPR formats, followed by Jones, Helu and Carter.

In non-PPR leagues, Jones is the No. 1 option, followed by McCluster, Helu and Carter.