Photo: Isaiah J. Downing, USA Today Sports

It's time to update my True Fantasy Points (TFP) math given what's happened in the first four weeks of 2018. If you're unfamiliar with how my TFP system works, here are the links to my preseason articles:

1. Quarterback TFP
2. Running back TFP
3. Wide receiver TFP

The Cliffs Notes version is that I calculate TFP by multiplying players' "true" efficiency stats by their opportunity, and then applying Footballguys' standard scoring system to the result:

1. For quarterbacks, my opportunity measure is pass attempts, and the efficiency stats I turn into "true" stats are Yards per Attempt (YPA), Touchdowns per Attempt (TDPA), and Interceptions per Attempt (INTPA).
2. For running backs, my opportunity measures are carries (in the running game) and routes run (in the passing game), and the efficiency stats I turn into "true" stats are Yards per Carry (YPC), Touchdowns per Carry (TDPC), Receptions per Route Run (RPRR), Yards per Route Run (YPRR), and Touchdowns per Route Run (TDPRR).
3. For wide receivers and tight ends, my opportunity measure is routes run, and the efficiency stats I turn into "true" stats are RPRR, YPRR, and TDPRR.

As an example, Marvin Jones has amassed 15 catches for 233 yards and 2 touchdowns, which translates to an Actual YPRR of 1.5 and an Actual TDPRR of 1.3% based on estimated routes run in 2018. And based on about 1,400 actual routes run in his Lions career, Jones' True YPRR is 1.7, and his True TDPRR is 1.1%, which means he "should" have 251 yards and 1.6 touchdowns on those 15 catches. If we apply Footballguys' standard coring system to both sets of numbers, we find that he's actually scored 35.3 points, whereas his "true" skill suggests 34.9 points (slight math discrepancy due to intentional rounding). This translates to a 0.4-point difference between standard points and TFP, which one can interpret as Jones being neither a buy-low or sell-high candidate. In essence, he's performing almost exactly on par with expectation.

So with everyone on the same page, find out which players are most likely to see their fantasy scoring pace slow down (or speed up) over the course of the next three months.

All tables below show actual standard fantasy points (i.e., "FBG"), TFP, and the difference between the two values for players that appear in the Top 300 of our Rest of Season rankings (sorted by the "DIFF" column for each position).

Quarterbacks

Below is the table for quarterbacks:

Sell High: Patrick Mahomes II II

No doubt, Mahomes has been great in his first four games as Kansas City's starting quarterback. However, his rate stats are completely unsustainable.

As the table shows, he's nearly 40 standard points ahead of where his "true" stats indicate he should be. For instance, he's currently throwing a touchdown on 10.1% of his passes, whereas the average for quarterbacks in the table is 4.9%. Given he's only thrown 173 passes with the Chiefs, these numbers translate to Mahomes' True TDPA being 5.0%. In other words, his Actual TDPA right now is more than double what his "true" skill suggests.

Similarly, Mahomes has yet to throw an interception in 2018. This, of course, means his Actual INTPA is 0.0%, which is significantly lower than his True INTPA of 2.4%.

Sell High: Jared Goff

Like Mahomes, Goff is currently benefiting from an Actual TDPA that dwarfs his True TDPA. Specifically, the latter is 4.9%, whereas the former is 8.2%. Even more absurd is Goff's 10.5 Actual YPA in 2018, which far exceeds his 7.6 True YPA.

In contrast to Mahomes, Goff has a reasonably large sample size, having thrown over 800 passes with the Rams, so these are arguably even larger statistical anomalies.

Buy Low: Aaron Rodgers

Rodgers is actually performing better than his "true" skills suggests when it comes to throwing interceptions (0.6% Actual INTPA vs. 1.8% True INTPA). However, he's underperforming his other two "true" rates by such a large extent that he still shows up at the bottom of the table. Specifically, based on a sample size of over 5,000 passes with the Packers, Rodgers' True YPA is 7.8, while his True TDPA is 6.0%. So far in 2018, his Actual YPA is 7.2, and his TDPA is 4.5%.

Perhaps losing Jordy Nelson this offseason has had a bigger negative impact than was believed at the time, but a stagnant running game and injuries to his current stable of wide receivers are also likely to blame. Once those factors work themselves out, Rodgers is poised to rebound.

Running Backs

Below is the table for running backs:

Sell High: Alvin Kamara

Kamara is on pace to post the most prolific receiving season by a running back in NFL history. But it turns out that it's his rushing stats, not his receiving stats, that are unsustainable going forward.

Last season, Kamara averaged 6.1 YPC so his 4.9 Actual YPC this season actually represents a good deal of regression to the mean already. The problem is that, with the exceedingly random nature of YPC and Kamara's rushing career in New Orleans comprising only 176 attempts, Kamara's "true" skill (4.4) hews much closer to the league average (4.3).

Likewise, scoring five touchdowns in 56 carries translates to an Actual TDPC of 8.9%. However, regressing this to the 2.8% league average means his True TDPC is less than half that (3.8%).

Sell High: Melvin Gordon III

Gordon has both of the regression indicators that Kamara does, plus one more. Namely, he's scoring receiving touchdowns at a rate four times what his "true" skill suggests. So far in 2018, Gordon's scored 3 touchdowns on 95 receiving routes run, for an Actual TDPRR of 3.2%, whereas his True TDPRR is only 0.8%.

Buy Low: Derrick Henry and Dion Lewis

Both of Tennessee's running backs are poised for an uptick in fantasy performance, but for slightly different reasons. And the difference makes perfect sense from an intuitive perspective.

Both Henry and Lewis are well below their True YPCs: Henry's at 3.0 Actual YPC compared to 4.3 True YPC, whereas Lewis is at 3.3 Actual YPC compared to 4.3 True YPC. Where the difference lies is in which kind of touchdown they're not scoring so far in 2018. For Henry, it's rushing touchdowns, as he has a 0.0% Actual TDPC compared to a 2.9% True TDPC, which means he "should" have about 2 rushing touchdowns right now; not 0. For Lewis, it's receiving touchdowns, as his 0.6% True TDPRR means he should have at least 1 receiving touchdown right now; not 0.

Wide Receivers

Below is the table for quarterbacks:

Sell High: Calvin Ridley

Ridley's actual YPRR of 2.3 is definitely high, but it's not wildly out of line with his True YPRR of 2.0 (which is in some elite company, by the way). Rather, Ridley's likely regression going forward is due to an Actual TDPRR of 5.2% being over three times higher than True TDPRR of 1.6%. Put differently, he should have 2 receiving touchdowns based on 116 routes run; he actually has 6.

Sell High: DeSean Jackson

Jackson's career renaissance through three games is likely to end. And while there exists a ready-made narrative explanation for it (i.e., the benching of Ryan Fitzpatrick), there's also a statistical explanation. Namely, Jackson's Actual YPRR of 4.2 ranks first among wide receivers in the table, whereas his True YPRR is "only" 1.9.

Because it was also alluded to in the Ridley discussion above, it's worth pointing out that a True YPRR at or above 2.0 can be considered elite. For instance, Julio Jones is No. 1 at 2.7 and DeAndre Hopkins is the lowest of this bunch at 2.0. Therefore, Jackson's True YPRR of 1.9 is probably closer to elite than you thought. Still, it's not the 4.2 that it is right now, so regression is highly likely, especially now that the Fitzmagic show is over.

Buy Low: Odell Beckham Jr Jr

Speaking of elite wide receivers as measured by True YPRR, Beckham is a candidate for vast improvement in fantasy efficiency going forward, as his 2.0 Actual YPRR is significantly below his 2.3 True YPRR. But that's not all. It's also the case -- perhaps even more importantly -- that his current total of 0 receiving touchdowns is a statistical aberration. Among wide receivers in the table, Beckham's True TDPRR of 1.7% ranks No.1, which means his skill suggests he should have scored three times by now.

Buy Low: JuJu Smith-Schuster

Like Beckham, Smith-Schuster is also scoring -- or not scoring -- at a much lower rate than his skill suggests. In fact, he's scoring at half his expected rate. Specifically, despite a Top 25 True TDPRR of 1.2%, he's only scored 1 touchdown in 192 routes run (0.5% Actual TDPRR).

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