"Coach Lupoi is a terrific young coach and a dynamic recruiter," Huskies head coach Steve Sarkisian said in a press release. "He will have an immediate impact with our team both on the field and in recruiting."
The sudden defection by the former Golden Bear defensive lineman could devastate Cal's star-studded recruiting class, currently ranked No. 12 nationally and second-best in the conference.
Lupoi had been Cal's closer on the recruiting trail, earning awards and national recognition for pulling the likes of wide receiver Keenan Allen away from traditional powers such as USC and Alabama.
His loss just two weeks before Signing Day could create a ripple effect across the West Coast.
Sacramento (Calif.) Grant safety Shaq Thompson, a five-star prospect who committed to Cal at the US Army All-American Bowl nine days ago, wrote on Twitter that "I have a lot of thinking to do," echoing sentiments of players pledged to or considering the program.
"It's a business. My family told me (I) have to do what's best for me," he added.
Lupoi was just as effective in developing linemen as he was recruiting them, helping turn Tyson Alualu and Cameron Jordan into first-round NFL draft picks.
Trevor Guyton earned second-team All-Pac-12 honors this past season.
Lupoi had been involved with Cal football for 12 consecutive seasons, arriving on campus as a player in 2000. He later served as a graduate assistant before joining the coaching staff full time in 2008.
Cal head coach Jeff Tedford was on a flight and unavailable for comment.
Cal Sports Digest will have more on this story as it develops.