Nicks hurt his shoulder in the Giants' win over the San Francisco 49ers in the NFC championship game. The Giants listed Williams, their fastest linebacker, with a foot injury.
"Just resting my body, getting my body back and ready. It's a little beat up," Nicks said.
Also out were center David Baas (abdomen-neck), linebacker Chase Blackburn (calf), backup cornerback Will Blackmon (knee), running back Ahmad Bradshaw (foot) and cornerback Corey Webster (hamstring).
Bradshaw and Webster have had their injuries for weeks and it has not stopped them from playing.
Giants coach Tom Coughlin expects all his injured players to be ready for the Super Bowl.
"Trying to be smart," Coughlin said. "Trying not to aggravate something that's there."
Backup safety Tyler Sash practiced on Thursday after passing the concussion protocol for a blow he took Sunday.