Leftwich, who is battling a sprained left ankle, was downgraded from "questionable" to "out" on the injury report. The sore ankle flared up last week, without warning, and did not improve during the week. Coach Jack Del Rio initially said after last week's loss at Houston that he did not feel the ankle was a factor in Leftwich's performance but then changed his mind after reviewing tape of the 27-7 defeat.
For now, there is no definitive timetable for Leftwich's return.
A fifth-year veteran, Garrard has started eight games in his career. He started the final five contests in 2005, while Leftwich was sidelined by a fractured left ankle, and posted a 4-1 record. The current ankle problem that Leftwich is experiencing is not related to last year's fracture, the Jaguars said.