Best, worst matchups by position

Don't forget I do a twice-weekly podcast called the Fantasy Underground, where Field "He Rolls Out Of Bed That Smart" Yates and I discuss what we've seen on film, and how it relates to your fantasy team. Subscribe on iTunes; that way you'll never miss a show! And while you're at it, follow me on Twitter at @CHarrisESPN. All right, let's get to today's topics:

Four in depth:

1. Best and worst matchups for quarterbacks. Now that we've passed the NFL regular season's halfway point and the fantasy playoffs are a month away, it's time to check in again on the Harris Metrics (self-designated trademark, desperately looking for a better name than this crummy one, feel free to tweet) to get a sense of which opponents are most and least inviting. To refresh in brief, rather than merely look at the Fantasy Points Against page that doesn't take schedule into account, the Harris Metrics (someone save me from that name, please) measure how far a given player is held above or below his moving average. In other words: It's more impressive for a defense to allow an average of 12 fantasy points to Peyton Manning, Drew Brees and Cam Newton than to allow an average of 10 fantasy points to Chad Henne, Ryan Tannehill and Carson Palmer.

First off, let's look at defenses that are stopping QBs and defenses that are giving it up to QBs. Note that at this point in the season, I'm now looking at the past five weeks rather than the entire year; what happened in September isn't particularly relevant anymore here in early November. Here are the friendliest defenses to opposing QBs, all of whom are more than one standard deviation from the mean:

You can read this data as: "Over the past five weeks, the Tampa Bay Buccaneers on average have tacked 6.8 fantasy points onto the five-week average of the QBs they've faced." Now, clearly the Oakland Raiders defense is dramatically affected by last week's crazy 45-point outburst by Nick Foles, which was out of character for them of late and which was more than 23 fantasy points above the average Philadelphia Eagles QB performance over the past five weeks. But too bad, these metrics are pitiless. And here are the defenses that have been hardest on opposing QBs of late:

Once again, Foles' Week 9 insanity seeps into these metrics, as the New York Giants get extra credit for not allowing huge outputs to the Eagles QBs both in Weeks 5 and 8. So it's fair to a bit skeptical about the Jints. (More on them below.) But these other defenses have legitimately been difficult for opposing QBs.

2. Best and worst matchups for running backs. Exactly one RB who has faced the Arizona Cardinals defense has matched his five-week fantasy-point average: Marshawn Lynch. He had 21 carries for 91 yards and a TD in Week 7's Thursday night game. That's it. That's the list. Daryl Washington has been the play-making force this unit lacked to begin the year, and Calais Campbell continues to be a stud. It's true that the team's linebacker corps has been hit hard by injury, and that's the kind of thing that can catch up to you quick. But as of now, they look like the league's toughest foe for an opposing rusher:

Going in the other direction, I presume you're not surprised that the Chicago Bears have been miracle workers for opposing rushers. With Henry Melton, Lance Briggs, D.J. Williams and Nate Collins out for the year and the team's desperation signing of Jay Ratliff last week, it's safe to say the Bears are candidates to get manhandled up front on a weekly basis. And the New England Patriots have similar woes, with Vince Wilfork and Jerod Mayo done for the season. (Again, I'm giving all the defenses who are currently more than one standard deviation away from the mean.)

3. Best and worst matchups for wide receivers. I always try to go a little lighter on basing too much analysis on the WR numbers. First, these numbers don't do the nuanced thing of breaking apart "No. 1 receivers" and "No. 2 receivers," something that's readily available all over the Web. So for instance, the Cleveland Browns grade out as a middling preventer of WR fantasy points, but when your top receiver gets trailed around the field by Joe Haden (as happened with Torrey Smith last week), life feels a little harsher than the numbers might indicate. (Though to be fair, Smith came on late in Week 9, and wound up with five grabs for 78 yards.) Next, and relatedly, when you're combining "all the WR points that Team X scored this week," that can often include a whole lot of ancillary weapons, and thus not necessarily directly reflect on a defense's ability to stop the WRs you care about. And lastly, the WR metric (and, for that matter, the QB metric) can look artificially strong because a team's defense is so poor against the run.

That's certainly the case with the supposed "best" stopper of wideouts, the Bears. On average, WR groups have had 6.8 fantasy points trimmed from their bottom lines by Chicago. But that's with Charles Tillman battling a knee injury and looking like a shadow of his former self, and two starting safeties who couldn't catch a cold. So I don't want to sell this unit as some fearsome group, especially if your WR plays on an offense that isn't likely to take advantage of the Bears' ugly run defense, and instead prefers to keep throwing. (I'm looking at you Matthew Stafford, Reggie Bush and Calvin Johnson owners in Week 10.) Anyway, here are the units against whom opposing WRs have graded out poorly over the past five weeks:

And here are three defenses on whom WRs have feasted most, again with the caveat that the Raiders just allowed a historic amount of fantasy points to the Eagles passing game:

One final question: Are the New York Giants really improving so much on defense over their past four games (they were on bye in Week 9) that they deserve to be on all three of these "bad matchup" lists? On first glance, I'm skeptical. The four games in question were:

• Week 5 versus Philadelphia: Michael Vick gets hurt early, the Giants focus on stopping LeSean McCoy (and do a good job), daring Nick Foles to beat them, which eventually he does, aided by three Eli Manning picks.

• Week 6 at Chicago: An ugly Thursday night game in which the G-Men bottle up Matt Forte effectively, but Jay Cutler has a super-efficient game and rarely takes chances, once again benefiting from Manning's turnovers.

• Week 7 versus Minnesota: The Josh Freeman game. Need I say more?

• Week 8 at Philadelphia: Vick gets hurt again, Foles is out with a concussion, so Matt Barkley has to play.

So yeah, there's some circumstantial evidence that indicates we don't have to tread super-lightly when our fantasy stars are up against the Giants. But having reviewed all that tape, I can say: The run defense is starting to look legit. Justin Tuck has played well over the past month, and the team is actually getting something out of former draft bust Linval Joseph, albeit in a part-time role. The worries that I have are that all three linebackers are a problem waiting to happen, including Jon Beason, who looks super-fried. But the fact that they contained McCoy, Forte and Adrian Peterson over the past month, even with extenuating circumstances, should at least convince us to reconsider this unit.

4. Best and worst matchups for defensive units. Finally, let's flip it around. I always like looking at the D/ST metric, because it's essentially a lineup of the NFL's best offenses, the ones you least want your defense to have to face (though clearly the Green Bay Packers are a lot less scary with Seneca Wallace under center):

And then it's a list of the most blunder-prone offenses, who give up turnovers, sacks and defensive or special teams TDs:

Here, it's fair to say, numbers about the Giants do not mislead, as Eli leads the entire NFL in turnovers, with 15 interceptions and two lost fumbles.

Four in brief

5. Jake Locker ... must-start??? I may have gotten more tweets about Locker than any other player this week, and my fellow ESPN.com rankers seem to regard Locker as a strong fill-in start even in shallow leagues. Why am I not there with Locker? Well -- and it feels as if I say this a lot -- I think too often we make our lineup decisions based on how we assume a game is going to play out. I think those interested in Locker see the matchup against the winless Jacksonville Jaguars and assume massive points for all Titans. And listen, Locker has a 27- and a 21-point game this season. Unfortunately, he also has a five- and a 10-point game this season. And while the Jags gave it up on the ground to Colin Kaepernick in London a couple of weeks ago, remember that they held Peyton Manning to 13 fantasy points four weeks ago in a competitive game, and also kept Philip Rivers to 15 points in a non-blowout. My worry with Locker is that he has Mendoza-line throwing accuracy and eight passing TDs in six games. Granted, he's got some running chops (two rushing TDs in '13); if you played out this week 100 times, there would be several where Locker went crazy, and maybe one of those will happen Sunday. But there also would be several where Locker played poorly enough to get the Jags their first win.

6. Don't get suckered in by Andre Brown just yet. He was my top new free agent find of the week, so it's not as though I hate Brown. In fact, he was on my 2010 Super-Deep Sleeper list, back when he was just a twinkle in Tom Coughlin's eye. I like the player. But I don't think the ESPN RB ranks accurately reflect Coughlin's comments this week, which have included the notion of easing Brown back into the team's RB rotation. Peyton Hillis is widely expected to lead this committee for a week (while Brandon Jacobs could be involved, too). Certainly, in the heat of the moment if Brown looks good, perhaps this notion gets thrown out the window. But I do believe that the plan is for the Giants to use Hillis a bunch this week. So while I absolutely advocate for adding Brown in all leagues, I'm reluctant to start him against the Raiders in Week 10.