How Much Does Calvin Johnson's Potential Retirement Affect Matthew Stafford?

Giving up the blanket from your childhood is not an easy experience.

Where'd you turn to when you saw too much of a scary movie? Blanket.

Who supplied the biggest patch of material when you wanted to create a fort in your living room? Blanket.

When you were in college, and the football team just lost another heartbreaker? Most of y'all probably dumped your blanket by then, but I don't easily detach from sentimental objects. So blanket.

For his entire NFL career, Matthew Stafford's blanket has been Calvin Johnson. No matter what kind of stickiness Stafford got himself into, Megatron was there to bail him out, usually in spectacular fashion.

Now, Johnson has reportedly told the Detroit Lions that 2015 was his final season. The team is making an effort to prevent that, but it looks like we've seen the last of the physical freak in Detroit.

Stafford is forced to deal with the possibility that he'll be without his most dependable target in 2016 and beyond. Ruh roh. That can't be good.

Let's take a look at what kind of impact Johnson's absence would have on Stafford using numberFire's Net Expected Points (NEP). This is the metric we use for both teams and players to quantify the expected points they add to the offense.

The reason we use NEP is that it better tracks the impact of each play. If we look at yards per attempt, that would mean a six-yard reception on 3rd and 5 is the same as a six-yard reception on 3rd and 7. In reality, that's not true. Using NEP can help qualify for those differences to better track the true impact.

With NEP as our guide, let's see how things line up for Stafford if he, indeed, is forced to move on without his 6'5", 236-pound, childhood blanket.

Johnson's 2016 Metrics

There's no doubt that Johnson wasn't quite his regular self this past season. However, his volume metrics were still impressive.

He finished the season ranked 10th among wide receivers in Reception NEP at 105.07. He was targeted 149 times, the ninth highest mark in the league, so it makes sense that he would rank among the best.

When we narrow the focus to a per-target basis, though, things don't quite look as glowing for Johnson. Here, he drops to 26th of the 48 wide receivers with at least 80 targets. He was ahead of guys like Larry Fitzgerald and Jeremy Maclin, but that's still not quite the Johnson we're used to.

The issue here is that wide receiver efficiency is heavily dependent on the quarterback. We can't truly track the impact on Stafford unless we compare Johnson to other players Stafford was targeting last year.

Still the Top Option

In looking at those numbers above, it would make it seem as if the Lions could possibly get by without Johnson on the roster. While that's still not out of the question, things get a bit more bleak when we zone in on just fellow Lions.

The best metric for comparing Johnson to his teammates is Target NEP. This will account for every outcome of every target that goes his way. If Johnson snags it, he'll likely have a positive Target NEP. If it's intercepted or falls incomplete, then the numbers will reflect that.

This table shows how the four Lions wide receivers who had at least 15 targets compared in this category in 2015. To qualify for the discrepancy in opportunities, I also included the Target NEP on a per-target basis. This is where Johnson seemed to excel.

This shouldn't be a major shock, but even at his advanced age, Johnson was the top receiving option on the team. That would seem to be important information.

Even when compared to the non-receiver skill-position players, Johnson's efficiency held up. The only player who had at least 20 targets and a better Target NEP per target number was running back Joique Bell (of course!), and he was only targeted 27 times. For his volume, Johnson led the pack.

Given Johnson's continued effectiveness, how wary should we be of Stafford heading into 2016? It could be a bit of tough sledding.

An Expected Dip in Efficiency

Even with Johnson in the mix this year, Stafford wasn't exactly setting the world on fire with his efficiency. Things got better as the season progressed, but the end sample left much to be desired.

Of the 46 quarterbacks who recorded at least 100 drop backs, Stafford finished 18th in Passing NEP per drop back. This put him behind Jay Cutler and Jameis Winston and right in front of Josh McCown and Brian Hoyer. Not exactly the most elite of company.

Let's go back to the numbers in the table above. If we take out the expected points lost on sacks, the Target NEP per target numbers are translatable back to quarterbacks. And they tell a pretty significant tale about what we should expect from Stafford.

When Stafford targeted Johnson, he averaged 0.32 Passing NEP per attempt. After taking out the expected points lost on sacks for all quarterbacks, that would put Stafford's efficiency this year between that of Tom Brady and Drew Brees, ranking sixth overall. When he targeted Tate, he would have ranked 24th. That's behind Blake Bortles, Brock Osweiler, and Ryan Tannehill. Not great, Bob!

One would assume that -- if Johnson does end up retiring -- the Lions would address this in the offseason. If they don't, the outlook for Stafford isn't going to be a good one.

Johnson may not have been the same monster he was in 2012. However, he was still the clear best option on the board. Without him on the field, these numbers make things look even worse for Stafford than we may have expected given the relative decline of one of the best of all time.