Whenever I think of teams trying to spend money in the NFL, my mind slips to a dark, dark place where Mike McCarthy is dressed as Macklemore in the "Thrift Shop" music video. Why does it go there? I don't know. I've stopped asking such questions.

The parallels between the video and the NFL run deep, though. If a team can get a running back that isn't going to cost as much as a Gucci belt, then you bet your britches they'll jump all over him. Somebody's gotta pay for the quarterback's inflatable swan pool toy.

However, at the same time, this strategy doesn't work as often as teams would hope. Sometimes when you pay for a clunker, you get a clunker. Because of this, the homies here at numberFire wanted to see which teams spend the most intelligently and get the most out of what they pay for. Leo Howell took a look at which teams had the most and least cost-effective quarterbacks in 2013. I, however, am a fan boy of the big uglies up front, so I wanted to see which teams had the most effective ground games last year.

In order to do this, I'll be using numberFire's Net Expected Points (NEP) metric. It's a measure of how effective an offensive is compared to a league-average team. For example, an NEP of 110 means that a team's offense would be expected to score 110 more points than the average team.

For this specific case, I'll be looking at each team's Adjusted Rushing NEP per play. This only takes rushing plays into account, and is adjusted based on the team's strength of schedule.

If you want to read more on NEP, you can click here.

At times, I will also refer to a player's individual Rushing NEP. This is just a measure of the number of expected points a player gained his team whenever he ran the ball. So, if a player gets a carry on 1st-and-10 and takes it for seven yards, he'll have a positive NEP on that play. If he gets stuffed for a two-yard loss, it'll be negative. For rushing, a positive NEP is tough for early-down backs because it's less efficient than passing the ball, and these rushers will typically only see short yardage gains. For reference, LeSean McCoy led the league in the stat last year at 37.12, and only 10 players with at least 200 carries had a positive Rushing NEP.

Whenever I reference the amount of money a team spent at a certain position, those numbers are coming from Over the Cap. If you're into stuff like this and have one/thirty hours to burn, I recommend checking it out. For this one, I'll be looking at what teams spent on running backs and offensive linemen in 2013.

With that, chillens, let's get to it. Which teams had the most and least cost-effective rushing attacks in 2013? Is Mike McCarthy's giant, pee-stained fur coat working? These are the questions the people want answered.

Most Cost-Effective Rushing Teams

It turns out that when your moth-ball-infested coat can truck a brudduh like Eddie Lacy can, life's pretty good. As you can see on the chart below, things were poppin' for the Packers on the ground last year, despite not spending a ton of dough. Where it says, "Total Spent," that refers to the total number of dollars that a team spent on running backs and offensive linemen in 2013.

Here are the most cost-effective rushing teams from 2013:

For some context, the highest Adjusted Rushing NEP Per Play in the league last year was the Eagles at 0.11, and the lowest was the Giants at -0.14.

The main reason the Packers excelled here was obviously Lacy. As a late second-round pick, he only counted for $616,802 against the cap. Among rushers with at least 200 carries last year, Lacy had the 10th-highest Rushing NEP at 2.32, right between Marshawn Lynch and Alfred Morris. That's not too shabby for a young pup.

All of this isn't to say that Lacy was the only reason the Pack mopped up this one. James Starks was actually stupidly efficient when he handled the ball last year. He had the fourth-highest NEP in the league at 17.20, though it was only on 89 carries. Part of this is because Starks' three touchdowns were from 32, 25 and 32 yards out, and that will jack your Rushing NEP way up. Either way, Starks had a great season. He even had a higher Success Rate (percentage of carries that result in a positive NEP) at 43.82 percent compared to Lacy at 42.46 percent. This was all with only a $655,075 cap hit to the team.

Chicago is on this list for a bit of a different reason. While Green Bay was able to save big with young and surprisingly efficient running backs, the Bears did it with the most inexpensive line in all of football.

Last year, the Bears spent a grand total of $10,071,052 on their entire offensive line. That's more than $7 million less than Jay Cutler will make in 2014. Wut. Three of the five starters on the line made less than $2 million, and nobody made more than Jermon Bushrod at $3,015,000. Again, having a rookie stud like Kyle Long helps, but this team got some crazy good production out of their backs considering how little they spent up front.

For Dallas, it's pretty simple: DeMarco Murray is not of this world. Even though he missed a couple of games last year, Murray still racked up the second-highest Rushing NEP in the league among running backs at 21.42. He kicked Jamaal Charles's tushy in every relevant rushing metric (Rushing NEP, Rushing NEP Per Play, Success Rate), and he did it all for only a cap charge of $810,938. If that doesn't get you a little weak in the knees, you best get yourself checked, my friend.

This year, Murray's cap hit does ramp up to $1,596,625, but it doesn't matter. If he can replicate the production he had last year (preferably without missing any games this time), dude will be worth every penny.

Least Cost-Effective Running Teams

Fun's over, kids. You got to see the beacons of hope for the other thrifty members of the NFL. Now, here come the heaping piles of poo that threaten to blot out the Sun with their stankiness.

Below are the teams that, despite spending a decent chunk of cash on their running backs and offensive line, couldn't get things cooking. This is money they could have spent on My Little Pony stickers or something useful, but instead they wasted it on inefficiency and sadness. It's an injustice to America.

The Giants were bad at a lot of things last year. Eli Manning had the worst Total NEP (which takes both passing and rushing into account) of any quarterback in the entire league, including cross-town rival for the honor, Geno Smith. It would be easy to say that Manning and the passing game were the weak part of the offense, but the ground game gave them a serious run for their money.

Despite having the seventh-most money devoted to running backs and offensive line, the Giants had the worst rushing game in the entire league. Their -0.14 Adjusted Rushing NEP per play means they lost 0.14 points every time they ran the ball. That's not generally the intent. They may have been better punting the ball on first down than running or throwing, but they may even find a way to screw that up.

The Titans and Seahawks are on this list for a very different reason. As their NEP numbers show, they were both better than average at running the ball last season. Party streamers and cake for everyone! But, in order to get there, they had to spend a boatload. Tennessee spent the most money of any team on running backs and linemen with the Seahawks checking in third place, yet neither had a truly dominant ground game.

The guy that really killed this number for the Titans was Chris Johnson. After the Titans cut Johnson, numberFire's JJ Zachariason wrote about how ridiculously overrated Johnson is based on his one shining moment in 2009. Johnson provided some fuel to that argument this year by posting a Rushing NEP of -12.63, the ninth-worst total in the league for a back with 200 or more carries, despite a roughly $10 million salary. That doesn't help the cause.

As I mentioned earlier, Lynch finished with the ninth-highest Rushing NEP among running backs with at least 200 carries with a total of 4.81. That's not bad. Once you add in Russell Wilson's 22.19 Rushing NEP, the Seahawks look like they're sitting pretty. However, if you take out Wilson's total, the team had a Rushing NEP (unadjusted for strength of schedule) at -12.61.

I realize that's partially unfair because the offensive line also affects how well Wilson can run the ball, but in general, the Seahawks rushing game was extremely mediocre last year. That's not what you should expect when you spend the third-most money in the league on offensive line and running backs. I'm not saying they were bad - I'm just saying they're not as good as they should have been given the resources dedicated to the positions.

In a league like the NFL, spending improperly can set your franchise back years (Oakland, anybody?). Striking gold on a later-round rookie serves a double purpose of making you look like a genius and giving you straight money trees to drop on other areas of need. But if you're going to make it rain on your offensive linemen and running backs, baby, you'd better be cranking out some serious yardage with that ground game. So, Mike McCarthy, go ahead and hit up the thrift shops, bromigo. Sometimes poppin' franchise tags and spending that $20 million in your pocket won't be freaking awesome.