The Patriots placed Pettus (ankle) on injured reserve Wednesday.
Pettus exited the second quarter of Sunday's 20-3 win over the Steelers with an ankle injury. The injury appears to be significant and will require Pettus to miss at least four games on IR before being able to return to the active roster. With Craig Woodson (shoulder) also injured, the team will likely look to sign or elevate a player from the practice squad to fulfill the strong safety role in Week 3 against the Jaguars.