According to Mike Garafolo of NFL Network, Key is kicking off his free agency tour with a visit to the Detroit Lions.
Key hasn't dismissed the possibility of returning to the 49ers. Although, the Bay Area team is unlikely to participate in a bidding war for the defender, should one start.
"I want to come back," Key told fans during an Instagram Q&A (h/t TheSFNiners). "S--t, they got to want me to come back. Well, they want me to come back. We got to see if the money right."
San Francisco has already lost two defensive linemen in free agency. Fan-favorite D.J. Jones signed with the Denver Broncos and Kentavius Street left for the New Orleans Saints. While Key might be next, he acknowledged in January that there was something different about the 49ers' locker room.
"A lot of teams say we care about one another, we want to see everybody successful and everything like that, but we really mean it over here," Key said. "It's really a brotherhood. And I don't want it to end."