Johnson, 32, signed a four-year, $19 million deal in 2012 and missed five games with hamstring and hand injuries in 2013. The Chargers will save $1 million with the move.
Free agent receiver
"Players have already started to reach out to me from other teams saying they would love for me to come join them," Nicks said. "I just want to make it clear that I want a long-term deal and I want to be happy. I'm excited about talking to teams and making it work."
Nicks earlier said he was open to a one-year deal.