The team also announced that practice squad wide receiver Darnell Jenkins has been placed on the practice squad/injured list. With the two open spots on the practice squad, the team signed wide receivers Robert Ortiz and Nick Moore.
Welker reportedly tore the ACL and MCL in his left knee during Sunday's loss to the Houston Texans. He finished the 2009 season with an NFL best and franchise record 123 receptions.
Williams, a former fifth-round pick of the Jacksonville Jaguars in 2008, joined the Patriots' practice squad on Nov. 10. He appeared in six games as a rookie before being released before the 2009 season.
Moore, the brother of New Orleans Saints wide receiver Lance Moore, is a rookie out of Toledo who spent time with the Minnesota Vikings after signing as an undrafted free agent. Ortiz is in his third stint with the Patriots since entering the league as an undrafted free agent out of San Diego State in 2006.