Matchups, volume, and a variety of other factors generally trump talent when it comes to fantasy football. As we saw earlier in the season with Melvin Gordon, volume -- particularly in the red zone -- often matters more than efficiency. Combining the two is how you come across the elite performers at each position.

The majority of the leaders in Total Net Expected Points (NEP) at the running back position are players who catch a lot of passes out of the backfield -- which makes sense, because passing is inherently more efficient than rushing. While efficiency matters, we need to factor in touchdown scoring when considering both positive and negative regression candidates.

This week, I've decided to include a couple tables that highlight players who have scored above and below league average.

Now, let's get to this week's Regression Candidates.

Negative Regression Candidates

Marcus Mariota, QB, Tennessee Titans

Marcus Mariota has erupted since Week 4, averaging 24.2 fantasy points per game -- which leads all quarterbacks in scoring in that span. He has been a weekly start through a string of favorable matchups, supplementing his passing performances with his legs. Mariota injured his ankle last week but is expected to play against the Green Bay Packers this week, although if his mobility is at all inhibited by this injury, it could take away a valuable element of his game. Given the offense's proclivity to run the football, Mariota should not be expected to throw for three touchdowns on a weekly basis.

Latavius Murray, RB, Oakland Raiders

Latavius Murray played about 50% of snaps for the second week in a row, but he scored a trio of touchdowns against a floundering Denver Broncos run defense. Murray is dominating the red zone opportunities on a high-powered offense, making him a valuable fantasy asset. He has rushed for a touchdown in all but two games this season -- and has scored on almost 44% of his red zone carries. He's as good of a bet to score as anyone, but it's hard to trust a player that is so reliant on touchdowns for his production -- particularly when math dictates that he should not be having quite the success that he is.

Cole Beasley, WR, Dallas Cowboys

When a team has a historically dominant red zone talent like Dez Bryant, the logical gameplan would be to throw it to him, right? Dak Prescott seems to disagree. The rookie has locked onto Cole Beasley at all levels of the field, turning the former afterthought into a consistent weekly fantasy option. Beasley has scored on two-thirds of his red zone targets to date, which is almost three times the league average rate. Given the sample size, it would be foolish to dismiss Beasley's work to date, but it would be fair to expect some regression in this area.

Cameron Brate, TE, Tampa Bay Buccaneers

Cameron Brate is tied for the NFL lead in touchdowns by a tight end with four, sharing his success with teammate Mike Evans. Brate has 42 targets on the season, which ranks 17th among tight ends and comes out to an average of approximately 5 looks per game. With a Tampa Bay Buccaneers running back seemingly getting injured every week, the Bucs have become increasingly reliant on the pass in the red zone in recent weeks. However, Doug Martin finally was able to return to practice this week and faces a string of soft run defenses in the upcoming weeks, capping the touchdown upside of low-volume options like Brate.

The chart below shows each running back with at least five red zone rushing touchdowns and the percentage of their carries inside the 20 that have gone for touchdowns.

The following table includes players who have caught at least 4 red zone touchdowns on 10 or fewer targets, and it is sorted by touchdown rate. The league average touchdown rate in the red zone is around 23%.

Positive Regression Candidates

The positive regression candidates all -- with the exception of Joe Flacco -- share a common theme. They've all played good football this season and have performed relatively well in fantasy, but have scored an abnormally low number of touchdowns for the volume they're receiving.

Joe Flacco, QB, Baltimore Ravens

Joe Flacco is on pace for just 12 passing touchdowns. As JJ Zachariason wrote on Twitter, no quarterback in NFL history has thrown for 4,000 yards with fewer than 17 touchdowns. So basically, Flacco is either going to face some positive regression, or compile one of the most unlucky campaigns for a quarterback in this pass-happy era. With an upcoming matchup against the Cleveland Browns -- the only team he has been able to throw more than one touchdown against this season -- positive regression is the safer bet.

Le'Veon Bell, RB, Pittsburgh Steelers

Up until Sunday's game, Le'Veon Bell had been performing extremely well despite not scoring a touchdown this season. The game plan against the Baltimore Ravens was designed to protect Ben Roethlisberger in his return from injury, and Bell found himself running into a wall of defenders every time he touched the ball. Since returning from suspension in Week 4, Bell is the only running back without a rushing touchdown among the 24 running backs who have at least 60 total carries. According to Graham Barfield, Bell should have roughly three touchdowns already -- but instead has none. As Big Ben gets closer to full health, Bell should be a monster.

Emmanuel Sanders, WR, Denver Broncos

Emmanuel Sanders leads the NFL in red zone targets and owns the largest target share of any player in the red zone in the league, but he has scored just two touchdowns this season. Even without the touchdown production, Sanders ranks 9th in Reception NEP and 14th among wide receivers in PPR scoring this season. There is major positive touchdown regression coming, but that's not the only reason to be excited about his prospects moving forward. The Broncos play the New Orleans Saints on the fast track of the Superdome this Sunday, giving the Broncos' passing game a huge boost.

Brandon Marshall, WR, New York Jets

Brandon Marshall is in a similar situation to Sanders. Like Trevor Siemian, Ryan Fitzpatrick has struggled at all levels of the field this season, but he has continued to pepper his favorite target -- particularly in the red zone. Marshall is second in the NFL in red zone targets with 17 -- trailing only Sanders -- but has caught just five of those passes for two touchdowns. Marshall is the alpha, number-one target who has run into poor touchdown luck that is bound to correct itself.

Jason Witten, TE, Dallas Cowboys

Jason Witten had his best game of the season on Sunday against the Cleveland Browns, moving him up to TE11 for the season (in standard leagues). Witten has served as Dak Prescott's safety blanket, but he has scored just 1 touchdown on 12 red zone targets through half of the season. Although Witten has never been an elite touchdown scorer in the past, his usage in this area of the field this year should lead to some natural positive touchdown regression.

This chart shows the running backs who have 10 or more red zone carries and 3 or fewer rushing touchdowns inside the 20 -- again sorted by touchdown rate.

The chart below shows players with at least ten red zone targets who are well below that league average red zone touchdown rate of 23%.