The Chiefs’ spear concept
The spear concept consists of two posts from one side and a deep cross/over from the other side. The two posts are essentially clear out routes as the play is almost always designed to go to the deep cross. They always ran the deep cross to the field. They seemed to prefer running it against man coverage as the deep cross gives the receiver a lot of time to separate, and also as he is aligned tight to the formation he will almost always have inside leverage.
The concept is similar to yankee (deep cross with a post on the opposite side), and like Yankee it’s best against single high coverages.
The play is generally used in conjunction with some form of 7 man protection as the quarterback needs time for the play to develop. The Chiefs had two main ways to give Mahomes’ time: the first was to use a ‘ride’ fake and to have their back up tight end stay in to protect the end man on the line of scrimmage (EMLOS). This is called full slide protection as each offensive lineman slides a gap over. The back has a protection check and then releases on his route. The second main way they protected it was to use what some call 4/5 jet. The difference between this and regular jet protection is that the tight end chips and the back also chips if possible after completing his protection check.
These protections were effective as Mahomes was rarely pressured.
I first learned this play from watching LSU, and of course, LSU learned it from the Saints.
They introduced a new variation in 2019 that they only used a couple of times but it is a better variation for spread teams as all five eligible receivers run routes. The main difference is that the second tight end runs a shallow cross rather than staying in to block. Also, the outside receiver on the weak side runs a mandatory outside release fade rather than a post. These two changes essentially make it weak side flood. This gives the quarterback a nice high-to-low read between the deep and shallow crosses.
Overall, the Chiefs had quite a lot of success using the spear concept and it was one of their go-to concepts when looking for a chunk play. However, they did have trouble using it against the Patriots as they threw interceptions on both of their attempts against them. The second one was an illustrative (last play in cutup) issue about the potential downsides of throwing deep crosses against man when the defender has help over the top as he can undercut it. This interception seemed to turn them off running it as they didn’t use it at all at for the rest of the 2019 season, so it’s difficult to project them using it more in the 2020 season.