We've hit the final four weeks of the NFL season. Here. We. Go.

After 13 weeks of the 2019 NFL regular season, savvy fantasy football owners are looking for opportunities to buy low and sell high on potentially unsustainable performances. We spend the entire offseason trying to predict what will unfold once the action starts, but now we can react to actual data and information.

By detailing both negative and positive regression candidates, the hope is that we will uncover some of the truths behind what we've seen so far this year.

Negative Regression Candidates

Kyler Murray, QB, Arizona Cardinals

It's been a strong rookie season for Kyler Murray, who currently clocks in as QB6 this year. Unfortunately, the advanced metrics and the fantasy playoffs may not go so well.

While he maintains a high ranking from a fantasy perspective, this performance has been built on his rushing, not his passing. Among quarterbacks with 150 or more drop backs, Murray ranks a lowly 26th (out of 35) with a Passing Net Expected Points (NEP) mark of 0.02.

The schedule is brutal as you advance into your fantasy playoffs -- the Pittsburgh Steelers, his opponent this week, have 29 takeaways in 2019, and they've allowed the fourth-fewest fantasy points to opposing quarterbacks.

Expect Murray to start backsliding soon.

Tom Brady, QB, New England Patriots

Yup -- we are going to bash Tom Brady and the New England Patriots. Things appear to be getting worse, not better.

After a disappointing Week 13 loss to the Houston Texans -- which really wasn't as close as the 28-22 score indicated, as the Pats scored two meaningless touchdowns down 28-9 -- the Brady boo-birds are getting louder and louder.

While he did break the mythical 300 passing yard mark this week -- his first time since October 10th against the New York Giants -- he is still struggling mightily. He sits only 20th in Passing NEP per drop back (0.07), and he ranks near the bottom of the league with an average intended air yards (IAY) at only 7.7.

It gets worse this week -- the Kansas City Chiefs rank fourth-best via our per-play metrics in 2019, so it could be another bad week for Brady.

Aaron Jones, QB, Green Bay Packers

Unfortunately for Aaron Jones, while the Green Bay Packers seem in a good spot to make the playoffs, it may not be due to his stellar play.

When we peek at the efficiency of the two runners in the Green Bay backfield, it's not a surprise that Jamaal Williams has been eating into Jones' workload. Williams has actually recorded a better Rushing NEP per carry mark -- albeit slightly (0.06 to 0.05) -- in 2019.

That leads to what we've seen in recent weeks, where Jones is losing valuable touches to Williams. Looking at Week 13, Jones grabbed 15 total touches, but Williams ate into the workload with 14 total touches of his own.

Don't count on Jones for a huge playoff run.

James Washington, WR, Pittsburgh Steelers

While he's recorded back-to-back 15-plus point fantasy games, there's too much volatility to consider starting James Washington in your fantasy playoffs.

He checks in impressively as the WR8 over the last month, though that's built on the strength of some very long pass plays -- his 209 receiving yards over the last two weeks can wet your whistle, but it's on only 11 targets. For a reference, his 23 targets over that period ranks only 35th.

Even though the Arizona Cardinals have allowed the fifth-most points to opposing wide receivers, that low volume, combined with being led by quarterbacks Mason Rudolph and Devlin Hodges, leaves Washington in a tough spot.

Positive Regression Candidates

Ryan Fitzpatrick, QB, Miami Dolphins

The QB5 over the last four weeks is Ryan Fitzpatrick. Just like we all expected, right?

With 71.84 fantasy points over that time frame, Fitzpatrick has been ballin' -- and the numbers reflect the same thing. While he's been sacked a whopping 17 times over those last four games, when he has time to throw, he's been brilliant, recording a Passing NEP per drop back mark of 0.14.

His schedule for the fantasy playoffs is absolutely delicious down the stretch, too -- as he will face some horrid pass defenses in the New York Jets (24th), New York Giants (27th), and Cincinnati Bengals (29th).

Stream Fitzpatrick and expect some big-time results.

Ryan Tannehill, QB, Tennessee Titans

After replacing the ineffective Marcus Mariota at quarterback, the Tennessee Titans have undergone a significant resurgence and are now looking at a playoff bid with Ryan Tannehill as their signal-caller. With five wins in their last six contests, not only have the Titans surged from a real-life perspective but from a fantasy one as well.

Part of Tannehill's effectiveness is his ability to take shots deep -- his IAY ranks as one of the league's best, clocking in at 9.0. If we take out his 11 sacks over the last three weeks, his 0.63 Passing NEP per drop back is off the charts.

His schedule, like Fitzpatrick's, sets up well, starting in Week 14 -- he faces an Oakland Raiders defense that ranks 28th against the pass and has allowed the fifth-most points to opposing quarterbacks.

Look for Tannehill to continue his solid run of play.

Derrick Henry, RB, Tennessee Titans

If there's a player that can dethrone the great Christian McCaffrey from the #1 spot in running back rankings, it's Derrick Henry, who continues his positive regression surge to the top of the fantasy charts.

Now, this may have seemed like a pipe dream early, as Henry broke the century mark only one time (in terms of rushing yards) over his first nine games.

But man, Henry has gone beast mode since then. He's eclipsed 100 rushing yards in each of the last three games, and he's gone for over 140 rushing yards in each of those three games -- scoring five touchdowns and logging a Rushing NEP per rush mark of 0.39. Wowza.

With the Oakland Raiders and Houston Texans -- who both rank in the bottom half of the league's rushing defenses -- on tap next, Henry could continue his ascension to the spot of the league's top runner.

Robert Woods, WR, Los Angeles Rams

It seems like the Los Angeles Rams and Robert Woods have heard our fantasy complaints loud and clear -- if he can just find the damn end zone, he will be rocketing up our leaderboards, and fast.

While his 39 targets ranks him fifth in the NFL over the last four weeks (despite playing only three games), Woods doesn't shoot up to the top of the wide receiver pool as he hasn't found the end zone over that same time frame.

But what's interesting is that quarterback Jared Goff has fared well against poor pass defenses this season, and he gets another porous passing defense in the Seattle Seahawks in Week 14.

With both the Seahawks and Cowboys coming up on the schedule, look for Woods to find the end zone for this resurgent passing attack.