Chancellor did not report to camp on Thursday with his teammates, but missing Friday's first practice will make him an official hold out.
NFL.com’s Ian Rapoport reported earlier this week that Chancellor wants to be paid more money and could hold out of training camp to angle for a new deal.
Chancellor has three more years remaining on his current contract and stands to make $4.6 million this season. He signed a four-year extension in 2013 after he was named to his second Pro Bowl. Chancellor was a Pro Bowl selection again in 2014.
Seahawks defensive end Michael Bennett was also reported to be considering holding out, but Bennett reported to training camp on Thursday.
Seattle's training camp will run through Aug. 19.
- Molly Geary