Sherman told NFL Media's Michael Robinson that he is not fully convinced Beast Mode's career is officially over.
"I don't put anything past him," Sherman said at Robinson's youth football camp in Mechanicsville, Va., on Saturday. "He's about as predictable as a pair of dice. So I don't try to call his plays. But obviously, it's going to be different.
"We got a little sample of it last year. ... I think we're prepared for it in some aspects, but you really never want to be prepared for that. You really would hope he comes back. In the back of your mind, you hope he comes back and plays another year."
Lynch, 30, did not formally announce his retirement, instead he posted a telling but cryptic message to social media with a photo of neon green and gold Nike cleats hanging. The message was first seen on Twitter during the fourth quarter of Super Bowl 50 on Feb. 7.
The Seahawks have placed Lynch on the reserve/retired list, signaling the official end of his nine-year NFL career.
Lynch appeared in only seven games last season because of injuries, totaling 417 rushing yards and three touchdowns on 3.8 yards per carry.
Lynch joined the Seahawks after a 2010 trade with the Buffalo Bills. He started 77 of 82 games for Seattle and ranks fourth on the franchise list in rushing yards (6,347) and rushing attempts (1,457), second in rushing touchdowns (57) and third in touchdowns (65).
With the Bills and Seahawks, Lynch totaled 9,112 rushing yards and 74 touchdowns on 2,144 carries.
As a sign of respect, Seahawks general manager John Schneider recently said he promised Lynch the No. 24 would not be used in 2016.
"One of my last conversations with Marshawn was that nobody was going to wear No. 24 this year in the regular season," Schneider said.
If Lynch changes his mind about retirement, the Seahawks retain his rights.