Leslie Frazier served as the Bills’ defensive coordinator from 2017-22, but he was away from the team last season and he has not returned for the coming campaign. Buffalo has a replacement in place (Bobby Babich), but it remains to be seen if he will call plays. 
Babich – promoted from the role of linebackers coach in January – has been with the team since 2017, and he drew coordinator interest from outside teams during the 2024 hiring cycle. This Buffalo gig represents his first DC posting in the NFL, however, and Babich has not called a defense at either the college or pro levels to this point in his career.
Head coach Sean McDermott called plays last year, and he said earlier this month that a final decision will not be made on that front until at least training camp. Whichever direction the team goes, the coach guiding the unit will face considerable expectations. To little surprise, though, Babich will receive the chance to handle play-calling duties this summer before McDermott elects to either hand over the reins or repeat his workload from 2023.
“There’s going to be intentionality on my part to make sure, whether it’s practice or preseason games, that Bobby’s given that opportunity,” McDermott said, via The Athletic’s Tim Graham (subscription required). “So it’s just a matter of when and for how long.”
It would come as little surprise if Babich were to operate as play caller during Buffalo’s exhibition games in addition to training camp practices. McDermott has plenty of experience in that regard dating back to his own DC tenures, and he guided the Bills to a fourth-place finish in scoring defense last year. The team has generally fared well on that side of the ball during the McDermott era (although their postseason performances have not matched regular season showings), and his familiarity with the role could help as a transition to plenty of new faces is made in 2024.
The likes of Tre’Davious White, Leonard Floyd, Tyrel Dodson, Jordan Poyer and (at least for now) Micah Hyde are no longer in the picture for Buffalo’s defense. One of the team’s top storylines will be their ability to fill the vacancies created by those absences, and the decision on play caller will of course be a key topic to follow during the summer. Babich will receive at least a brief look before McDermott makes a final decision.