The 6-foot-3 Toomer underwent surgery Wednesday, a day after an MRI revealed the knee has a ligament tear.
"I didn't think anything of it," Toomer said. "It was very disappointing when I got the MRI. This happened before on the right knee, so I kind of knew what it felt like when it happened."
The injury occured against the Houston Texans last Sunday.
This season, Toomer, a 10-year veteran, scored three touchdowns on 32 receptions for 360 yards.
In his career, the Michigan product has 47 touchdowns on 561 catches for 8,157 yards.