Every now and then, somebody profoundly intelligent in one field of human endeavour says something that makes the world question how wide-ranging their intelligence is.
"American football is much more technologically advanced than soccer," Julian Nagelsmann recently said. "The quarterback has an earpiece to hear his coach; we absolutely need that."
It seems pretty plausible that the German manager was just spitballing and wasn't actually setting out a plan, but let's examine the idea further anyway. The idea didn't get wide coverage, but what it did get was negative. Pretty heavily so.
However, let's take this notion and run with it. Not because I want to give managers the ability to micromanage, but because interrogating an idea like this can be fun. Sometimes you can get something novel out of nonsense.
The German's quote itself shoots itself in the foot: American football is not like association football. For one, you don't have a quarter-back; for another, you don't have breaks in play. Maybe you'd want to earpiece up the captain, but captains in football aren't always the players who pull the strings of tactics and tempo on-field.
Another sport which might be an interesting comparison is Formula One, which has earpieces but without the NFL-type breaks between plays. Drivers can communicate with their engineering and strategy teams, and that can be useful.
Sometimes a change of weather or an incident somewhere will dramatically change the pit-stop strategy, or the driver needs to be informed of some issue with the car they need to manage. Information can be quickly and succinctly relayed.
The best exchanges though, as a viewer, are the ones where the drivers just tell their engineers to fuck off.
Realistically, I think the way that tactical earpieces would work in football would be for them to only (or at least primarily) used in breaks of play, to relay relatively simple changes in shape or approach. "Switch to a three in midfield", "their left-back's having a bad game, let's send more long balls right at them", "be quicker pressing their defensive midfielder". All the stuff that already is being relayed to players mid-game, but that only happens when they have time to jog over to the sidelines when someone (usually a goalkeeper) is receiving (possibly unnecessary) treatment).
Given that managers can already tell their players what to do, the tactical element probably isn't enough to get a push behind earpieces. However, I think there are a number of other ways that earpieces could be used to add something to football.
Innovation Number One: Concussion detection
Now, this is the kind of 'bullshit science that gets sales' option. A consensus statement at an international conference for concussion in sport in 2016 said that "reported mean peak linear and rotational acceleration values in concussed players vary considerably". For various reasons, "The use of helmet-based or other sensor systems to clinically diagnose or assess SRC cannot be supported at this time."
This being said, I believe in science and all that stuff, so I feel like, one day, maybe you could be able to detect 'possible concussion impacts' from earpieces worn by players. We made it to the moon with less processing power than is in an iPhone and all that.
Also, if used in training, they could potentially monitor the allotted number of 'higher force' headers that players in England are supposed to be limited to each week.
Innovation Number Two: Player scanning data
I'm not sure if it's unfair to call 'scanning' a buzzword, but it's certainly a very popular concept to talk about at the moment. There is a whole field of research about it -- about how it makes players effective, and about what makes 'good' scanning.
The data, though, would be difficult to collect. This recent research paper relied upon watching clips of players. Can you imagine?? Watching players?? (These last two sentences should be read in the voice of Vinny Thomas). Imagine if you could sync an earpiece sensor to the vest-worn sensors, knowing where the head is looking in relation to the torso at every moment.
Innovation Number Three: Player orientation data
Thinking about it, earpiece sensors might not help that much with this. The current vest-packs that players wear don't tell you where a player is facing, just where they're moving. But if you could calibrate an earpiece sensor to know where 'north' of the pitch is, you could presumably do that for the vest-packs too. But an extra sensor couldn't hurt, and we need as many spurious benefits to sell these things, so it's going in the brochure.
Innovation Number Four: Mindfulness
We know that there are some players who struggle to perform in front of large crowds or in big moments. This is a human response. Maybe they could press a discreet button on the earpiece and get some breathing exercises piped into them, or some distracting music to get them in the zone.
The highly-paid elephant in the room
Now, one of, if not the, biggest obstacles to earpieces being used in football is the players themselves. It took long enough for the vest-packs to become standard, and they're fairly unintrusive. Imagine being asked to put sensors (somewhat) inside you.
A pretty compelling case would have to be made to them that this was worth their while, and not just another stick that coaches could use to beat them with. I'm also intrigued as to whether the bundle of use-cases I've provided might be less convincing to them than being presented with just Nagelsmann's idea. I'm sure different players would be more and less responsive to different possibilities.
There's also an important question, apart from the use cases, of how comfortable and secure the earpieces would be. Jonathan Wilson wrote off Nagelsmann's idea because he thought it unfeasible that earpieces would stay in, and maybe he's right. I'm no ear scientist.
Do I see the earpieces happening, even after all of this interrogating of the idea? Not really. I suspect that concussion detection would be so patchy, and so infrequently needed, that it doesn't provide much of a bonus; that the bonus of coaches chatting to their players isn't a worthy trade-off for wearing something in your ear for an hour and a half; and that players would be unconvinced by the need for data on their scanning.
But hey, we've all been wrong before.
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 "[...]maybe you could be able to detect 'possible concussion impacts' from earpieces worn by players." || F1 earpieces already have accelerometers in them, with the manufacturer's website saying that data is used to help make improvements to neck and head restraints. This is slightly different to the one-off forces involved in concussions, but it's at least something down a similar path.
 "This recent research paper relied upon watching clips of players." || Some studies cited by that paper used headbands to detect head movement, which is a step towards automated data collection but isn't something that would realistically be used in real-game scenarios.