Is Matthew Stafford Too Dependent on Calvin Johnson?
There’s a well known assumption around fantasy football circles that Matthew Stafford’s success is dependent on whether Calvin Johnson plays. This is understandable as Johnson is arguably still the best wide receiver in the game and any quarterback forced to play without his best weapon will surely see a dip in productivity. At a glance, Stafford is averaging 17.394 fantasy points per game in the 77 games he’s played since 2009, and in the six games without Calvin Johnson, Stafford is averaging 14.273 fantasy points per game, and 14.904 fantasy points in the five games Johnson missed in the past two seasons. Here’s the overall breakdown:
|Mean Fantasy Points||17.39||14.27|
We observe that there is a difference between the two means, and it appears to be fairly large. Being a statistician and a data analyst, I’ve decided to test whether this difference in our two means is actually significant using a significance test. We do this by accepting that an assumption is true and testing that assumption. In our case, we’ll assume that Matthew Stafford’s mean fantasy production is equal to his fantasy production when Calvin Johnson is not on the field. Our next step is to test whether the difference is actually considered “statistically significant”. We do this by using a formula which creates a metric that observes the difference between our sample mean, which in our case is the Stafford’s mean fantasy points without Johnson, and our population mean, and takes into account the amount of deviation and our sample size. What comes out of this calculation is a z-score of -2.304, which means absolutely nothing to the lay fantasy player, but allow me to explain. What this z-score can give us is a probability of obtaining a value as low or lower than our sample mean of 14.273, if our population mean is 17.394. The probability we obtain is approximately 2.12%, and being that the probability is less than 5%, in statistics we would declare the difference in means as statistically significant.
The analysis tells me that Stafford clearly does not perform as well when Calvin Johnson is on the field. However, necessary with all statistical analysis, qualitative observations are necessary before the decision making process. Stafford finished the 2014 season with 251.58 points in standard 4-point passing touchdown leagues, which was good enough for 15th among all quarterbacks, notably finishing behind Jay Cutler who played in 15 games. He finished 2013 with a slightly better finish of 278.90 fantasy points for 7th among quarterbacks. We do not know whether or not Calvin Johnson will be missing any games in 2015, but we do know that one thing is true, and that is that he is not getting any younger. Owners of Johnson and Stafford will be delighted if Johnson misses no time this season, but he is definitely trending in the wrong direction as he’s missed two games in 2013, and three last season. In Calvin’s absence in 2015, Golden Tate emerged as Stafford’s go-to guy. Tate averaged 13.3 targets in games where Johnson wasn’t on the field, which is a clear boost from the 8 targets per game he receives when Johnson is playing. However, I don’t need to be a football expert to convince you that Calvin Johnson is a much bigger playmaker than Golden Tate, and his impact on the field can not quite be replaced by Tate’s presence.
The most alluring factor leading owners to drafting Stafford in the past was volume as Stafford has finished in the top 5 in passing attempts in the past two seasons. This has helped Stafford pretty much default into the top 10 in fantasy in years past. However, while Stafford has not been a turnover machine finishing 19th among qualified quarterbacks (350 pass attempts) in interception percentage, he just hasn’t produced the touchdowns. In the four seasons where Stafford has started all 16 games, he has finished with more than 30 touchdowns just once. For somebody who drops back as many times as Stafford, you would hope that 30 touchdowns would be very much a reachable mark.
Stafford is currently being drafted as the 11th quarterback off the board, with an ADP of 104 in the 9th round. Frankly, I’d rather take a chance on the 12th quarterback Ryan Tannehill with an ADP of 106 or even the 15th quarterback in Teddy Bridgewater with a current ADP of 126 in the middle of the 11th round. Stafford lacks upside at a position which is seemingly teeming with potential, and as the analysis spelled out for us, appears too heavily dependent on a single playmaker. Consider avoiding Stafford on draft day, I certainly will not be drafting him this season.