The San Francisco 49ers held on against the Arizona Cardinals in their 28-25 Thursday Night Football victory that moved them to 8-0. While their record may still be unblemished, their vaunted defense just took a big hit as an MRI revealed that linebacker Kwon Alexander suffered a torn pectoral muscle.

Alexander was a big-money offseason addition to the team that was coming off a knee injury. However, San Francisco was proven right during the first half of the 2019 NFL season as he was a huge reason for the defense’s performance to date.

Last night, the Cardinals scored an 88-yard touchdown after Alexander exited, which made it a one possession game late.

Without Alexander it will be interesting to see if anyone else can step into his cleats. He is all over the field for defensive coordinator, Robert Salah and made the big plays when needed. He injured himself stopping Kenyan Drake one-yard short of a first down on a 3rd and 17 play in the third quarter.