Outside linebacker Dee Ford became the Chiefs' latest player to not be retained for next season.
The Niners are expected to give Ford a multiyear deal in the range of five years and $87.5 million, the source said.
The Chiefs are making significant defensive shifts this offseason, and the primary losses have been the team's two outside pass rushers in Ford and Justin Houston.
Ford was also Pro Football Focus' highest-rated pass rusher off the edge. Alexander, 24, will receive up to $54 million over the next four years on what has been viewed as a team-friendly deal. According to Terez Paylor of Yahoo Sports, a herniated disc limited Ford to just two sacks in six games in 2017, which quickly halted the momentum of his 10-sack season in 2016.
"You have to have a guy who can close out games, close out halves", general manager John Lynch said at the combine when talking about the need for better pass rushers. However, an average annual value of $17.5 million puts Ford third among linebackers, and third among defensive ends. He has recorded 380 combined tackles, seven sacks, 22 passes defensed, six interceptions, a touchdown, and six forced fumbles through his four National Football League seasons.
Ford, 27, recorded 13 sacks and 29 quarterback hits in 2018.
San Francisco has been searching for a player on the outside fitting that description since it parted ways with Aldon Smith in 2014.
This is a great move for the 49ers who can have some flexibility at the No. 2 pick if they choose to pass on Bosa or Allen and prefer to look at other positions, such as defensive tackle Quinnen Williams.
But the 49ers also run a 4-3, though it's different from most.
This trade is huge for the 49ers because it solves a long-term need for the team, and frees up some more opportunities for the team to make during the 2019 NFL Draft. The guaranteed money and potential outs are what matter most though.