Concussions are the biggest and most pressing issue the NFL, and football in general, is facing. Participation in the sport is steadily declining among kids. As we continue to learn more about football’s long-term health effects, the future of the NFL looks to be more and more uncertain.

On the inaugural Deep Coverage podcast, Kevin Clark took a look at why the game is so brutal. What if the plays that coaches choose to call are part of the problem? To understand the issue, he took a look at two different NFL offenses: Bill Walsh’s West Coast offense and Don Coryell’s “Air Coryell” attack.

To listen to the full podcast, check out the episode here. This transcript has been edited and condensed.

Kevin Clark: Around the early 1970s, Cincinnati Bengals [offensive coordinator and] assistant coach Bill Walsh developed what eventually came to be known as the West Coast offense. When the team suffered an injury, the Bengals were forced to start a much less talented passer than their usual quarterback. Walsh saw that the replacement quarterback didn’t have much arm strength, so he designed an offense to basically minimize the long pass from the game plan. A typical play type consists of a receiver moving shorter distances than most NFL offenses and oftentimes coming horizontally across the field. This is the perfect execution of the West Coast offense.

About a decade before Walsh, Don Coryell, then a college coach, invented an offense that was essentially the opposite. His scheme, dubbed “Air Coryell,” was popularized in the NFL in the 1970s when he became a head coach for the St. Louis Cardinals and San Diego Chargers. The key to the Air Coryell offense is the deep pass, which oftentimes involves the receiver running as far down the field as possible.

Coaches still rely on these offenses today. They are the backbone to many modern NFL playbooks.

Last year, a group of researchers published some fascinating findings in the Orthopaedic Journal of Sports Medicine about these two particular [kinds of] plays. I spoke with one of the coauthors: Masaru Teramoto.

Masaru Teramoto: The first thing that I realized is that the concussion rates actually differed between [the] West Coast offense and the teams with the other types of offense, which was actually surprising and I thought first that the concussion rates would be lower for the teams adopting a West Coast offense — but that wasn’t the case.

K.C.: The data Teramoto and his colleagues gathered examined concussions reported during the 2012 to 2014 NFL regular seasons. They found that teams who adopted the West Coast offense suffered more concussions than those teams who adopted Air Coryell. In fact, [players in the West Coast offense] suffered more than double the number of concussions on average, per season, than players using the Air Coryell. It’s astonishing to think that one type of play calling is linked to a higher rate of concussions, but it might make more sense if you think about the fundamentals that make up both offenses.

M.T.: The West Coast offense typically uses the lateral passes. So … it may be that the receivers are [not] aware of whether or where the hit comes from, and if the offensive player is not aware or not prepared for the hit, that might increase the risk of a concussion.

K.C.: This is an interesting theory to say the least. I reached out to Chris Nowinski, cofounder and president of the Concussion Legacy Foundation, to get his thoughts. He gave me this scenario.

Chris Nowinski: If you consider that player-to-player impacts and especially helmet-to-helmet impacts are the biggest cause of concussions in football, then if you have two people running in the same direction or three players running in the same direction, the most likely reason for concussion would be falling and hitting your head on the turf. But [in that scenario] you’re almost never going to be put in a position where you have two people running in opposite directions at each other and causing a big collision.

K.C.: In addition, the study also outlines that players involved in the passing game are much [more likely] to suffer head injuries than linemen or linebackers. This was surprising. Students of history would assume the forward pass would be the safest thing — that’s because the forward pass solved one the game’s darkest eras of injuries.

In the early 20th century, an alarming number of players were dying playing football. It reached epidemic levels. According to the Washington Post, “at least 45 football players died from 1900 to 1905.” The sport was in danger of being outlawed. Even the president at the time, Teddy Roosevelt, demanded change. A series of meetings led to new rules and in 1906 the forward pass made its debut. The game became open, and less brutal. It’s still common belief to this day that the pass game is much safer. So why did Teramoto’s study find the opposite to be true?

To hear more — including former NFL head coach Brian Billick’s perspective — check out the full podcast.