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.

While efficiency matters, we need to factor in touchdown scoring when considering both positive and negative regression.

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

Negative Regression Candidates

Matthew Stafford, QB, Detroit Lions

Matthew Stafford is currently 15th in the league in red zone passes, but he has the fourth-highest red zone touchdown rate, throwing touchdowns on 28.9% of his passes inside the 20-yard line. Theo Riddick has been an improved runner this year, but the Detroit Lions lack a consistent interior running game -- particularly near the goal line. This has helped lead to Stafford's current ranking as the eighth-best fantasy quarterback -- a result fueled by touchdowns in close. These touchdowns can be fickle and hard to predict, and his 5.7% touchdown rate -- which is his best mark since 2011 -- is probably unsustainable.

Ryan Mathews, RB, Philadelphia Eagles

Philadelphia Eagles coach Doug Pederson claimed that Darren Sproles would be his lead back prior to Week 10, so naturally it was Ryan Mathews who received the lion's share of the workload in Sunday's game against the Atlanta Falcons. Mathews has been effective this season when he's actually being utilized, but not only is his usage inconsistent and difficult to predict, but he's scoring touchdowns at an unsustainable rate. Mathews is currently tied for third in the NFL in red zone rushing touchdowns, but he has received by far the lowest market share of carries inside the 20 (54%) of any of the other rushers in the same ballpark as him in terms of red zone scores. Assuming he goes back to the low-volume role he's seen most of the year, Mathews is still going to be very touchdown dependent.

Mike Gillislee, RB, Buffalo Bills

Mike Gillislee has actually been a viable flex option in fantasy in four of the last five weeks, but all of his usable performances have come on the heels of a rushing touchdown while spelling lead rusher LeSean McCoy. McCoy was playing through an injury leading up to the bye week, but he should be closer to full health after getting two weeks of rest. In Rex Ryan's run-first offense, even the backup running back will handle moderate volume, but expecting a runner to score on limited touches every week is a dangerous game and not particularly likely.

Donte Moncrief, WR, Indianapolis Colts

Donte Moncrief was the beneficiary of an insane amount of hype this offseason as a big-bodied receiver in what projected to be a high-scoring offense. Based on his career splits in games with a healthy Andrew Luck, much of the praise was warranted. Unfortunately, the hype train skidded to a stop early in Week 2 when Moncrief went down due to injury. He has scored a touchdown in each of his healthy games this season, realizing some of the promise that owners foresaw back in August, but there are causes for concern. He only has a total of 22 targets in his three healthy games, has yet to eclipse 10 targets in a game and has scored on three of his five red zone targets. That conversion rate is strong and not a total fluke -- see Dez Bryant as an example of a player who has maintained success like this throughout his career -- but Moncrief is receiving just 11% of the target share in the Indianapolis Colts' offense this season. Because of the low volume, sustained touchdown success isn't likely.

Rishard Matthews, WR, Tennessee Titans

Rishard Matthews has scored in every game since supplanting Tajae Sharpe in the starting rotation at wide receiver, and Matthews has a touchdown in five of his last six contests. It helps that his quarterback is currently throwing touchdown passes at a historic rate, but Matthews is also not receiving anywhere close to requisite volume for the amount. Over those past six games (since Week 5), Matthews is averaging just 5.5 targets. As JJ Zachariason mentions in this week's 15 Transactions column, Mariota has a 9.4% touchdown rate since Week 5, and Peyton Manning had an 8.3% touchdown rate during his historic 55-touchdown season. While Mariota has certainly developed into a very good quarterback, the rate at which he's throwing touchdowns simply isn't sustainable, which will negatively impact all of his pass catchers.

Vernon Davis, TE, Washington Redskins

Vernon Davis became an integral part of the Washington Redskins offense when Jordan Reed suffered a concussion in Week 5. Since that point, Davis has not been held below 50 yards receiving and has scored a touchdown in two of those four games, totaling at least 13 PPR points in each game. Still, though, he has yet to top six targets in a game and has averaged just 4.5 targets a game during this hot streak. Davis is for real and has become an integral role player in Washington's offense, but the big plays and touchdowns will be inconsistent.

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 at least ten targets and a below average red zone touchdown rate. The league average touchdown rate in the red zone is around 23%.

Positive Regression Candidates

Colin Kaepernick, QB, San Francisco 49ers

Colin Kaepernick predictably shredded the New Orleans Saints two weeks ago, but rather than crashing back down to Earth against the Arizona Cardinals, Kaepernick actually surpassed his fantasy output in the last-minute loss. Kaepernick is averaging 57 rushing yards per game and has been a top-eight fantasy quarterback in each of his last two games, and this week, he faces a New England Patriots team that has been pretty fantasy friendly to opposing signal callers. Additionally, even though the San Francisco 49ers like to run near the goal line, Kaepernick has attempted just two passes inside the 10 yard line this season in his four games, which is bound to regress to the mean.

James Starks, RB, Green Bay Packers

No Green Bay Packers running back has scored a touchdown this season, which is shocking even when considering the struggles that Aaron Rodgers and company have faced this year. In James Starks' return on Sunday, he played the majority of the backfield snaps, which continues a trend of seeing Ty Montgomery phased out of the backfield rotation. The Packers have claimed that this was due to Montgomery being on a snap count, but it's unlikely that he would have been on the field with Brett Hundley in garbage time if that were truly the case. Despite Starks' ineffectiveness this season, he's still the primary runner on a team that spends plenty of time in the red zone. At some point, a running back will score at least one touchdown, and it looks like that will be Starks.

Julian Edelman, WR, New England Patriots

Julian Edelman has been a favorite target of Tom Brady for years. Since Brady's return from suspension in Week 5, Edelman has 44 targets over a five-game span, putting him at a total of 71 for the season. Despite the volume, Edelman has scored just one touchdown this season. Although he owns a 26% market share of the red zone targets in the New England Patriots' offense, that has resulted in just eight targets because of the reliance of LeGarrette Blount near the goal line. Details of Rob Gronkowski's injury have been murky and contradictory, but if he misses a game, Edelman will be a favorite target of Brady in scoring situations.

Stefon Diggs, WR, Minnesota Vikings

Stefon Diggs has been the focal point of a sputtering Minnesota Vikings offense since Norv Turner resigned as offensive coordinator. There are 11 receivers in the NFL who have been targeted on at least 25% of their offense's red zone passes, but Diggs is the only one that has not scored inside the 20-yard line this season. He actually has just two touchdowns this season on 81 total targets. However, Diggs has 13 receptions in each of his last two games, getting a staggering 29 targets in that stretch, and he has spent much more time in the slot recently. Per Scott Barrett, Diggs has lined up as a slot receiver on 69% of his snaps over the past four weeks, compared to just 43% over the first four weeks. Many top corners don't travel to the slot, allowing the Vikings to take advantage of their best playmaker in advantageous matchups. This week, Patrick Peterson is slated to follow Diggs into the slot, but it's not as daunting a matchup as it looks on paper -- Peterson has allowed a touchdown once every 6.1 targets in the slot as opposed to one every 22.3 outside for his career, according to PFF.

Eric Ebron, TE, Detroit Lions

Eric Ebron missed three games due to injury, but he hasn't scored a touchdown since Week 1. Even though Stafford and the Lions have slowed down a little bit offensively, Ebron has played some of the best football of his career in each of the last two weeks. Before the bye week, Ebron caught seven passes in consecutive games on an average of nine targets per game. Although he's never been an elite touchdown scorer, he's had a high floor recently due to the volume of targets he's been receiving, and the mismatches he creates due to his size will usually put him in favorable situations on the goal line.

This chart shows the running backs who have 10 or more red zone carries and 2 or fewer rushing touchdowns inside the 20 -- again sorted by touchdown rate.

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