Of course they do. Don’t be stupid.
Maybe the best part of football related discussions is that because the NFL is comprised of 32 teams, that all cycle through a number of skill position players every year, there are always examples of players that don’t conform to whatever rule, simply because of the power of numbers. Want to prove the point that you can draft a good receiver late in the draft? I guarantee there will be an example of that. Want to prove that a short QB can be effective? There will be an example of that. Want to prove the point that you can run and play defense, and still win a championship even though the NFL is now a passing league? We’ve seen examples of that and will probably see more in the future.
But just because you can illustrate an exception to a rule doesn’t mean that the rule doesn’t have value. Just because there will be any number of examples of players with slow 40 times that excel, doesn’t mean that 40 times don’t matter. To put it another way, a single player a trend does not make.
Why aren’t there any receivers in the NFL that run 5.0 40 yard dashes? If 40 times don’t matter then why doesn’t the distribution of receiver 40 times extend out that far?
Why did Bill Belichick say this about the prospect of converting basketball players to tight ends:
We’ve seen those guys through the years — guys with football backgrounds than end up playing basketball. I’d say I’ve had many conversations with [former Head] Coach Knight about that when he was at Indiana. I would say that the big thing for most basketball players is, in general, they’re quicker than they are fast. When you get out there and time a lot of those guys in the 40-yard dash, they’re slow. They might look fast on a basketball court, but we have such a much bigger field that vertical speed, especially for those positions — there aren’t many linemen playing basketball so you’re talking about skills guys, receivers and DBs, those type of positions, that most of them don’t have the speed that we, at our level, they don’t have the speed to play.
The average NFL career is something like 3 years, so we’re presented with a steady stream of players of various sizes and speeds that make their way through the NFL. Most of the top tier receivers are big and fast, but some aren’t. If NFL teams engaged in an annual re-draft of wide receivers, the first picks would be something like Calvin Johnson, AJ Green, Josh Gordon, Brandon Marshall, Dez Bryant, and then maybe this year Antonio Brown would make it onto that list. But does Antonio Brown’s inclusion on that list for the current year prove that you shouldn’t dismiss slowish/small receivers, or does it prove that the most likely place to find a real #1 WR is by starting with the group that is fast for their size? Does Barack Obama’s election as President illustrate that a black man is just as likely to be elected President as a white man?
When I hear someone say that 40 times don’t matter I tend to think that the person either doesn’t spend any time looking at the big picture (i.e. broad trends) or doesn’t care about the big picture. That’s how you end up with people saying that 40 times don’t matter. They focus on outliers and ignore that players that experience multi-year success in the NFL tend to fit into the group that is fast for their size. Not every player does, just most.
Having said all of that, it’s probably worth noting that if NFL teams are looking for an exploitable edge, they probably aren’t going to find it in 40 yard dash times. As Shawn Siegele illustrated, it’s probably the case that teams already take 40 times into account when they draft and they might actually place too much emphasis on them. Or they probably don’t adjust for player size at least when they do take 40 times into account. Player size is probably an exploitable issue. Scheme adjusted college production (market share) is probably an exploitable issue. But 40 yard dash times are already pretty well reflected in how teams draft.
So do 40 yard dash times matter? Of course they do. But a player’s draft slot matters too and since draft slot will be indicative of both physical attributes and also will incorporate opportunities for playing time, obsessing over 40 times might not be the most efficient thing that you can look at when studying NFL receiver prospects.