The NFL identified seven teams in 2017 that had a higher incidence of preseason concussions than the others and "did a targeted intervention with those clubs." 

"In six of those seven clubs, the numbers did go down," Dr. Allen Sills said. "Those seven clubs had 23 practice concussions as a whole in 2017, down to nine in 2018."

Overall, the league said, preseason concussions were down from 91 in 2017 to 79 this year, and there were zero on kickoff plays.